A 128-b rapid single-flux-quantum (RSFQ) Advanced Encryption Standard (AES) encryption accelerator based on bit-slice architecture is proposed for the first time. Unlike the traditional methods, the method of looking up only one 256-B table to complete the entire AES round function is proposed. The proposed method can reduce nearly 50% of the hardware cost compared to the traditional method. The simple lookup table, shift, and xor operations are used in the proposed accelerator where one 256-B table needs to be stored for lookup table operations. The RSFQ logic circuits of the proposed accelerator are designed and simulated at the logic level. It consists of 136 558 JJs based on the Open Dataset of CONNECT Cell Library for AIST ADP2. The simulation results show the proposed accelerator works correctly.