Phlebitis is a common complication of clinical anti-malignant arrhythmia intravenous medication, mostly due to inflammatory reaction caused by irritant drugs or hypertonic fluid entering the vein and stimulating the vessel wall, causing vasoconstriction caused by dehydration, hypoxia, congestion, edema, clot thrombosis of the endothelial cells and stimulating the intima. It is also caused by chemical inflammatory reaction of the local venous wall due to the long duration of the intravenous tube. There is also a local venous infection caused by the aseptic operation during the infusion process or repeated multiple punctures of the blood vessel. The local symptoms are redness, swelling, burning pain and red lines along the vein, forming thrombophlebitis and peripheral superficial phlebitis in severe cases. Methods: 4 layers of sterile gauze soaked in 50% magnesium sulfate solution are applied wet to the lesion, the wet area is larger than the red, swollen and hard parts, then a layer of clean and odorless cling film is wrapped in the outer layer, and an ice pack is applied cold to the outer layer, and a long strip of gauze is used for proper fixation, and the ice pack is replaced in time when it becomes soft or hot to maintain the cold state, once a day, for 6 h each time. Efficacy criterion: local pain disappears within 24 h Effective: pain disappeared, redness and swelling subsided, vascular elasticity recovered; Effective: pain disappeared, redness and swelling reduced significantly, vascular elasticity recovered within 72 h; Ineffective: pain did not disappear after 72 h, redness and swelling did not reduce significantly, vascular elasticity recovered poorly. Phlebitis determination criteria. Phlebitis stage: Stage I: phlebitis skin redness, pressure pain is obvious; Stage II: veins are red, hard and striped, pain to touch is obvious; Stage III: veins are reticulated red, swelling is obvious, burning, pain, affect the patient’s rest and sleep. The mechanism and advantages of 50% magnesium sulfate ice compress for phlebitis : (1) 50% magnesium sulfate is hypertonic solution, Mg can activate the protein activating enzyme and ATPase of cells, improve the permeability of cell membrane, stabilize the membrane potential, make the tissue edema subside in a short time, dilate the local blood vessels, increase blood circulation, improve the endothelial function of blood vessels, so as to achieve the purpose of local anti-inflammation and swelling; 25% magnesium sulfate is routinely used Wet and cold compress treatment method, some data show that this method is partially effective for patients with stage I phlebitis, and the effect is slow, and some are even invalid. (2) hot compress can make capillary dilation, but at the same time magnesium ion can also make capillary dilation, resulting in local capillary dilation in a short time, nerve endings increased sensitivity, pain aggravation, and infiltration into the tissue interstitial irritant drugs rely on the concentration difference of rapid absorption of water, easy to make the edema area increased. (3) ordinary 50% magnesium sulfate room temperature wet compress can not play a rapid effect of swelling, the patient puncture site pain is obvious, and cold compress therapy can reduce pain, but at the same time, magnesium sulfate wet compress can relieve local skin itching, burning, Gu should use wet ice. (4) ice can make local vasoconstriction, blood flow slows down, reducing cellular activity and metabolism, thus controlling the spread of inflammation and reducing tissue swelling and pain. Cold can inhibit the activity of cells, slow down the conduction of nerve impulses, reduce the sensitivity of nerve endings, reduce the permeability of blood vessel walls, reduce pain by reducing exudation. (5) This wet ice method, to reduce the direct contact with the skin ice bag to bring skin irritation, and the process is simple, and not waste drugs. In the magnesium sulfate gauze wrapped outside a layer of clean and odorless cling film, slowing down the evaporation of water, delaying the magnesium sulfate gauze dry and crystallization time, but also to prevent wet clothing. Precautions for care: pay attention to the observation of local blood circulation in the process of wet ice, to prevent frostbite; ice bag temperature increases, must be replaced in a timely manner; properly fixed ice bag, to prevent the removal of the ice part; magnesium sulfate gauze such as want to dry or crystallization to be replaced in a timely manner.