Abstract: In this paper, completely independent and bottom-level design is conducted by utilizing FPGA device, realizing conversion from fixed-point to floating point. A completely new method is proposed for such realization to output data by taking 3 clock cycles. In this method, subtraction calculation instead of logarithm calculation is adopted, occupying 1 % logic resources and avoiding the restrictions of using IP core and laying a foundation for follow-up ASIC design.