In past few years, optical encryption attracts much attention. Aiming at investigating the influence of parameters used in optical encryption on security and providing theoretical support, this paper addresses relation between the parameters and security. A simulating system is designed and developed. Then, it gives some simulation and analysis of a two-dimensional code identity and evaluates the correctness of the algorithms. It also discusses security influence of parameters in the encryption system, such as diffraction distance, wavelength, random template, and focus length. Simulation results show that the wavelength has more influences on security than other parameters do, and that there exist a nonlinear relation between the parameters and security. Finally, it gives some topics for further research.