To solve the problem that several C language executable modules without source code exist in the corecontrol- system program of 2.4 m wind tunnel which may severely hinders the future upgrade of the system, software reverse engineering techniques were adopted to develop the new sub-stitutional module. Methods and procedures, debugging scheme through which the new modules were developed are depicted in detail and the actual control curve of the new program is also presented. The testing result data show that the control accuracy of flow field and model attitude is equal or better than that of the old software, and the newly developed modules has been put into use in the wind tunnel testing, so the development of the software is successful.