The invention discloses an optical signal encryption/decryption system based on time lens imaging. The system comprises time lens imaging sub-systems. Each time lens imaging sub-system is composed of an input section optical fiber, a time lens and an output section optical fiber. The second-order dispersion phi''<2> of the output section optical fiber is opposite to the second-order dispersion phi''<1> of the input section optical fiber, namely the''<2> is equal to -phi''<1>. The amplification factor of each time lens imaging sub-system is M=phi''<2>/phi''<1>=-1. In all 0 code periods of time of pump light sequence streams, time lens effects will not be generated and signal sequences in covered periods of time of pump light are kept unchanged. In all 1 code periods of time of the pump light sequence streams, the time lens effects are generated and the signal sequences in the covered periods of time of the pump light are inverted. According to the optical signal encryption/decryption system based on time lens imaging provided by the invention, optical signals can be encrypted and decrypted, and the security of the system is high.