Objective:To provide morphology basis for anterior sacral operation.Methods: On 50 human cadavers,the anterior sacral veins were observed by dissection and clearing methods.Results:In 76.0% of the cases,the middle sacral vein was single and assumed an inconstant location.Its tributaries may communicate with the rectal venous plexus,the internal vertebral venous plexus and the lateral sacral veins.In 70.0% of the cases,the lateral sacral veins were double on each side.The tributaries of the lateral sacral veins may anastomose with those of the middle sacral vein on the ventral surface of the sacral vertebrae.The numbers of the transverse anastomoses were 5.82±0.32 on the left and 5.37±0.41 on the right.Conclusions: To avoid massive hemorrage during anterior sacral operation.particularly in rectectomy,attention should be paid to the distribution of anterior sacral veins.