Fifty-four rats that had been used as models for lymphedema were divided into nine groups to observe the changes of lymphatic contractility in pathologic conditions at varying postoperative days. The changes of the lymphatic contractility were divided into three stages in this paper: In the first stage, the lymphatic contractility was impaired by high intralymphatic pressure, but the morphology of its wall was normal and it could recover its function if the pressure was decreased. In the second stage, the blocked lymphatic lost its contractile function partially or completely because its wall thickened and fibrosed, but the newborn lymphatics possessed contraction function and could be anastomosed. In the third stage, most lymphatics had lost their contractile function because of severe fibrosis. The fibrosis of the tissue even blocked the growth of the newborn lymphatics. In this stage, therefore, it was unsuitable to do a lymphatic-venous anastomosis. It can be concluded from the experiment that lymphatic contractility should be considered before performing a lymphatic-venous anastomosis. The lymphatic that still has contractile function should be selected for lymphatic-venous anastomosis.