Abstract: To address the problem of low fidelity of simulated targets in passive electromagnetic modulation， an AFSS co-modulation method is proposed for radar target simulation based on the periodic intermittent modulation of Active Frequency Selective Surface （AFSS）. Firstly， the distance distribution of the target is determined based on the radar signal parameters and AFSS periodic intermittent modulation signal parameters， and then the phase of AFSS modulation signal meets the co-regulation condition to generate a simulated target with high fidelity in the distance upward direction. The basic principle of AFSS periodic intermittent modulation is given in the paper， and the conditions of AFSS cooperative modulation are derived theoretically. Finally， simulations are carried out to verify the feasibility and effectiveness of the method. The results of the study show that the simulated targets with high fidelity can be generated by the cooperative modulation of incident waves by AFSS targets. This co-modulation method makes up for the shortage of radar feature modulation of a single AFSS target and achieves high fidelity of the simulated target， and the dynamic change of the simulated target signal can also be achieved by controlling the modulated signal parameters. The method can also be extended to the cooperative modulation of multiple AFSS targets to realize the dynamic simulation of multiple targets in large scenarios. Therefore， the method proposed in this paper provides a new idea for passive electromagnetic modulation-based radar target simulation， and also has theoretical guidance for the next research of cooperative modulation method for imaging radar target simulation.