To evaluate the efficacy and safety of electrochemotherapy in treating venous malformations. Electrochemotherapy was applied to 665 patients with venous malformations of limbs and trunk, and 505 cases were followed up for half to 6 years. In this study, 228 male and 277 female patients were involved. Diagnosis was made by clinical manifestations and magnetic resonance imaging. The platinum electrodes were inserted into tumor through a trocar with plastic insulating cannula percutaneously and connected with the electrochemical therapeutic apparatus in anodes and cathodes separately. Then electricity was given. The treating voltage is 6-12 V and volume 100-180 mA, the total electricity used is in general 80-100 coulombs per 1.0 square centimeter of tumors' area. The treating time was usually from several dozen minutes to over 2 h depending on the size of the tumor. The severe cases which needed to be treated once again usually were operated after 6 months. The primary efficacy end point was defined as an improvement of patients' symptoms and a reduction in size of tumor 6 months after treatment. Effects were divided into 4 grades, and the efficacy rate decreased from grade 1 to grade 4. The efficacy turned out that 30.1% (152/505) of patients was classified as grade 1; 46.3% (234/505) as grade 2; 19.0% (96/505) as grade 3 and 4.6% (23/505) as grade 4. Electrochemotherapy shows special superiorities in treating venous malformations. It might bring a confirmed clinical efficacy with the advantages of less injury, quick recovery, simple operation and less complications.