The content of rotenone in leaves of Tephrosia vogelii and the extract time were determined by extracting purple variety leaves of T. vogelii repeatedly with benzene and chloroform as solvents by cold dipping method. It was showed that the precise content of rotenone in T. vogelii leaves was 0.69%. When the leaves of T.vogelii were extracted for 2 times and 3 times with benzene by cold dipping, for 2 days each, the extract rate of rotenone was 66.37% and 76.47%, respectively.