To meet the realtime performance demand of the booster’selectrichydraulic loading simulator,the realtime control system was developed based on QNX.The cycle of the control system was set precisely by using accurate timing property in QNX RTOS.The real-time control system was developed based on server/client model to improve the realtime performance.MUTEX and CONVARDS(Conditional Variables)were applied to synchronize threads.The booster loading test results show that real-time control system control cycle can be fixed at 0.5 ms;problems that the read/write data error and logical error in multiple threads system have been solved;loading accuracy performance meets the demand of practical engineering projects.