Objective To compare the effect and safety of using Rivaroxaban to prevent deep venous thrombosis(DVT) at different time in the perioperative stage. Methods There were 150 hip replacement patients in our hospital from January 2014 to October 2016. Based on the admission criteria, they were randomly divided into 4 groups. The patients in the group A used Rivaroxaban 72 h before operation. The patients in the group B used Rivaroxaban 48 h prior to the surgery. The patients in the group C used Rivaroxaban 24 h...