Abstract: Currently, in public researches about SM4 power attack, the power traces are generated by computer simulation or software implementation. However, this is different with hardware implementation which is used in actual. A research of a SM4 algorithm hardware implementation is given out, which is applied in market. we download the Verilog code to a SAKURA-G board, and collect the power traces when it actually operates. Correlation Power Analysis method is used to analyze the leakage of the input of the S-box in the first round, the output of the S-box in the first round and the output registers of the first round. We recovered the sub-key of the first round. By the same method, we can recover the sub-keys of round 2-4, and eventually get the 128-bit key.