In simulation systems of radar and jammer established with conventional methods, the systems are often difficult to expand and have low efficiency due to the close coupling. An improved method is proposed to solve this problem from three aspects. Firstly, the signals transmitted from the radar and jammer, instead of the received signals, are used as the signals transferred between them. Secondly, the radar publishes the transmitting signals one period earlier than the event time stamp and postpones the processing of signal for one period. Thirdly, the signal descriptors, rather than the digital signals, are transferred between radar and jammer. An analysis is made to the parameter setting of simulation time step and lookahead time. The effectiveness of the improved method has been verified by simulation experiment. The proposed method decreases the information dependency between radar and jammer, reduces the times of data interaction between them, saves the network overhead and improves the expandability and efficiency of the simulation system.