Directional modulation technology is one of the hot spots in the field of physical layer security communications in recent years. The existing researches study the synthesis algorithm of the directional modulation signal based on uniform phased arrays according to the different performance requirements of the application scenario. Those synthesis algorithms do not have universality under different performance requirements. To solve this problem, a synthesis algorithm of directional modulation signals based on sparse array is proposed. In the algorithm, the array element position of the sparse array is first solved by the forwardbackward matrix pencil method. Then, the corresponding optimization problem is established according to the performance requirements of the directional modulation signal. Utilize the objective function and constraints to unify different performance requirements into the same optimization problem to solve the array excitation. Simulation result shows that the proposed algorithm is better than the uniform arraybased directional modulation signal synthesis algorithm in the adaptability of transmitter design for different application scenarios.