The digital circuit of USB to RS-232 bridge controller is designed; HDL procedure of digital circuit module is downloaded to the FPGA verification board. A driver of the controller which works under the Windows XP is developed using softwares such as DDK, VC6.0, and the virtual COM is realized. Under driver and relevant cooperation of hardware environment, expected the function succeed of the controller is realized in the FPGA. This bridge graft device can be used in the data transmission between serial interface of the mobile phone and USB interface of the computer, reaching the effect of verification.