Recently, the weakness of existing compressive sensing process from the perspective of the chosen-plaintext attack has been discovered. To enhance the security and performance of compressive sensing process, double random phase encoding (DRPE) based block compressive sensing has been designed, which is a chaos-based random phase encoding in fractional Fourier domain for each image block. Moreover, this article presents a combined compressive sensing and optical image encryption method. The experimental results demonstrate that the proposed encryption method not only achieves high security level but also has comparable performance with existing encryption methods.