A new encryption algorithm of virtual optics is proposed based on computer-generated hologram and double random phase encoding system. The algorithm uses two-way double random phase encoding system which has same random phase masks but different parameters to achieve. In the encryption process,the plaintext is modulated by the first way double random phase encoding system,and its in-line hologram is superposed on a reference beam that generated by another double random phase encoding system,the ciphertext is the outcome of its filtering. The plaintext is recovered by calculations in reverse order of encryption process. Analysis proves that the virtual optics algorithm is valid. Computer simulation shows that the algorithm has a strong ability to resist the attacks of chosen-plaintext and ciphertext-only.