Protein 3+ may be caused by physiological reasons such as fever, strenuous exercise, or pathologic reasons such as damage to the glomerular filtration membrane, tubular reabsorption disorders, and overflow proteinuria. 1. Physiological reasons: physiological proteinuria is more common in the case of strenuous exercise, fever, etc., the patient’s kidneys have no organic lesions, no special treatment, after resting, the urine protein can usually turn negative. 2. Pathologic causes: (1) Damage to glomerular filtration membrane: glomerulonephritis, podocytosis, etc., resulting in damage to the integrity of the glomerular filtration membrane, reduced permeability, proteinuria, resulting in protein 3+. (2) impaired tubular reabsorption: lesions in the renal tubules, resulting in reduced reabsorptive power, can not absorb the glomerular filtration of protein, resulting in protein excreted in the urine, also protein 3 +. (3) Spillage proteinuria: in the blood circulation, a large amount of small and medium molecules of abnormal proteins appear, exceeding the reabsorption capacity of the renal tubules, resulting in abnormal proteins being excreted from the urine, and protein 3+ appears. Protein 3+ may also be caused by other reasons, if the patient found positive urine protein, it is recommended to go to the regular hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to targeted treatment or therapy.