In order to increase the I/O ports and the quantity of Pulse Width Modulation(PWM) in Hardware In Loop(HIL) simulation platform of dSPACE, an extension method based on Field Programmable Gate Array(FPGA) for dSPACE is presented. By constructing the data bus and the instruction bus between dSPACE and FPGA, the command table module, I/O extension module, the PWM generator module, A/D sample preprocessing module and data processing module are constructed on the FPGA, and the corresponding control models are constructed in MATLAB/Simulink. The dSPACE control on the FPGA extension modules and data exchange are implemented by the proposed method. Experimental results indicate that the proposed extension method can save the resource of the dSPACE platform, increase the dSPACE operating frequency , and enhance the function of the dSPACE as well.