A dual channel encrypted free-space optical communication system based on compressive sensing and tilted fiber grating is proposed. This approach not only greatly reduces the data acquisition volume, but also enhances the security of the system since the data transmitted in the free-space is encrypted. Besides, our proposal adopts low-bandwidth and low-cost photodetectors and analog-to-digital convertors, decreasing the data acquisition volume and the cost of data transmission. Also, the approach utilizes the tilted fiber grating with a 45° tilted angle as the free-space light emitter, free-space light lateral diffraction device, and polarization-sensitive device, simultaneously. The utilization of 45° tilted fiber grating greatly enhances the systematic integration, reduces the volume of the system and improves the energy efficiency of the system. A demonstration shows that two 1 GHz and 3 GHz sinusoidal signals are employed for the 3.9 m free-space data transmission with data compression ratios of 16% and 8% achieved both in the time domain and frequency domain.