Microelectronics Security - In this paper, we propose a Chaotic Probability Constellation Shaping (CPCS) method in Free-Space Optical (FSO) communication to enhance security and improve the performance of the transmission data. Gather as many points as possible in the middle via chaotic controlling. The influence of turbulence on the signal transmission can be attenuated to the minimum. In the simulation, a ratio of 56Gb/s 16-QAM signal is transmitted 1-km space channel with an attenuation index of 10dB/km. The CPCS technique can improve almost 0.5 dB optical signal noise ratio (OSNR) performance @10-3 BER than that of the related original signal. Simulation results indicate that the proposed method not only enhances the security but also improves the BER performance.