Objective To recognize and reevaluate the pathologic anatomic classification of ventricular septal defect （VSD）. Methods From January,2002 to October,2004,119 patients less than 10kg of body weight with simple VSD whose pathologic anatomic classification was determined by preoperative echocardiography and ascertained during surgery were choosed randomly. Results （1） There were fihy-one patients with perimembranous VSD （diameter 0. 6±1.0 cm）, 8 VSD situated in the membranous septum （diameter 0. 5±0.4 cm）, 21 VSD extending to inlet （diameter 0.8±0.5 cm）, 14 extending to outlet （diameter 1.0±0. 6 cm） and 8 extending to trabecula （diameter 0. 8±0.6 cm）. In this group, accessory tricuspid valve tissue was formed in 14 patients（diameter 0. 5±0.3 cm）. （2） Twenty-one patients had conoventricular VSD （diameter 1.2±0. 8 cm）, among them 13 VSD had muscle margins, 8 extending to membranous septum, 14 had septal band hypertrophy, and 5 had subaortic stenosis. （3） Twenty-six patients had subpulmonary VSD（diameter 0.8±0.8 cm）, 18 VSD lay immediately below pulmonary valve, 8 had muscle distant from pulmonary valve, 20 lay completely below pulmonary valve, and 6 lay below pulmonary valve and aortic valve. （4） Ten patients were atrioventricular canal type or inlet VSD （diameter 1.2±0.8 cm）. （5）Eleven patients had muscular VSD, among them 3 were single ,and 8 multiple （diameter 0. 4±0.3 cm）. Conclusion It will be more clinically significant that VSD is classified into perimembranous, conoventricular, atrioventricular canal or inlet, muscular and subpulmonary artery or conical types.