The operation of short-turn buses will affect the operation state of full-length buses． The reliability of bus operation system can be improved by properly designing a short-turn departure strategy． Given the operation of short-turn buses，a bus operation state model was established． And the departure strategy was designed with the cu- mulative sum ( CUSUM) method． In addition，based on the real-time IC data of bus No． 973 in Beijing，the influ- ence of different short-turn bus departure strategies on the operation state of full-length buses and passenger's average waiting time were studied by numerical simulation method． The simulation results show that the bus depar- ture strategy developed by this method can not only improve the bus operation reliability，but also greatly reduce the passenger＇s average waiting time; improper departure time arrangement have a negative impact on the operation reli- ability of other full-length vehicles．