The invention discloses an EDAC (Error Detection And Correction) check code generation method of a 8-bit-width external memory controller. The method comprises the following steps: firstly, generating an aligned executable program dat file; according to the dat file and an address bit width, calculating a maximum address of a memory; then, calculating the line number of check codes; when the total volume of data bits and the check codes is smaller than or equal to the volume of the memory, beginning to calculate the check codes; writing data in the original dat file and the check codes which are newly generated into an output file, wherein the original data bits are arranged in a positive sequence from a file header, the check codes are arranged in an inverted sequence from a file end, and the middle part is supplemented with 0. The inverted sequence storage of the check codes corresponding to the data bits in the memory can be realized, numerical values on all address lines when the processor reads the check codes are set as 1, the check codes are read in the inverted sequence from the tail end of the memory so as to be convenient and simple, pin numbers can be saved, internal logic units are reduced, and processor performance is improved.