Foot pus ulcers are commonly caused by the following reasons: first, diabetic foot, which is common in patients with long-term diabetes, and poor blood sugar control, resulting in vascular and neurological lesions in the lower limbs, causing the foot easy to ulcerate, not easy to get better, which requires timely control of blood sugar and regular drug replacement therapy. Second, trauma leading to infection, when trauma, if not timely clean up the wound, it will lead to foot infection, which needs to go to the hospital for surgical debridement treatment. Third, vasculitis caused by, when the lower extremity arteries or veins sclerosis and long-term existence, will lead to poor blood supply to the foot, will cause local ulceration, can have purulent fluid drainage out, which need to stop smoking, quit drinking, and need to give vasodilators and other drugs for treatment, and even some patients need to be amputated. Fourth, there are some rare causes, such as severe fungal infection of the foot and other cases. In short, if the infection persists and does not get better, you need to go to the hospital promptly to clarify the cause.