The invention provides a CPU instruction type hardware Trojan detection method based on a hamming distance. Firstly, an initial state CPU instruction is set, whether the instruction is a Trojan instruction or not is detected, and if the instruction is not the Trojan instruction, the initial state CPU instruction is expanded with the hamming distance as 1 to obtain an instruction set; secondly, the instructions are detected, it means that a CPU contains instruction type hardware Trojan if a Trojan instruction exists, if it is detected that the current instruction set does not contain the Trojan instruction, the hamming distance is added by 1, instruction expansion and sampling are carried out to obtain an instruction set, the detection instruction of the last step is returned, and it is judged that the CPU contains no instruction type hardware Trojan if no Trojan instruction is detected when the hamming distance is equal to the length of the CPU instruction. Compared with a traditional traversal method, all instruction positions are traversed at the same time for all triggering digits possibly contained in a traversal instruction, the testing times are greatly reduced, and CPU hardware Trojan triggered by a single instruction position and continuous instruction positions can be quickly and effectively detected.