An electro-optic intensity chaotic communication system is designed by combining two electro-optic delay feedback loops with parallel structures. By injecting chaos into chaos, a more complex chaotic waveform is generated to enhance the chaotic complexity and the communication system confidentiality. In this design, MATLAB and OptiSystem software are used to simulate the system, which solves the problem that OptiSystem software can't simulate the optical feedback loop. The mature laser and binary sequence generation modules in OptiSystem software provide energy and input signals for the system. The electro-optic delay feedback loops are realized by the MATLAB program, and the signal transmission in optical fibers is completed in the OptiSystem software. The article introduces how to use MATLAB and OptiSystem software to realize the co-simulation of chaotic systems. Numerical simulations show that the proposed method is feasible to simulate the optical feedback loop, and the simulation results are in good agreement with the theoretical values, which prove that the chaotic signal is generated.