A new method of antenna aperture sharing for communication and radar system is presented on the basis of the sparse array antenna and staggered sub-array theory.An analysis is made to the key indicators of the radar and communications with a shared aperture.Two key indicators are chosen as optimization objectives:the maximum peak side-lobe level of the radar array patternand the communication channel capacity of Multiple-Input Multiple-Output (MIMO) communication system.The array element position optimization problem under given array element number and aperture size is put forward.After setting a preference degreethe optimization problem is transformed into a single-objective optimization problemand a solving method based on genetic algorithm is given.Simulations and analysis prove the feasibility of the proposed optimization method,and the optimization curves for different preference degrees are given.