Superficial varicose veins of lower extremities is a common venous condition clinically. The incidence of varicosity increases with age. The development of minimally invasive technology leads to wide application of foam sclerotherapy in the treatment of varicose veins. Foam stability, the key in foam sclerotherapy, is closely related to the therapeutic effect and safety. At present, polydocanol sclerosant is commonly used for sclerotherapy. Studies have shown that stability of polydocanol foam is affected by multiple factors such as temperature, gas composition, liquid-gas ratio, concentration of sclerosant, surfactant and preparation. This article mainly reviews recent research on the stability of polidocanol sclerosant foam with a view to providing evidence for safe and effective clinical application of polydocanol sclerosant foam.