Abstract: Based on FPGA, an I/F convert circuit with high linearity and large range is designed by optimizing the logic control module of the typical I/F convert. The test results show that the linearity of positive and negative paths of all the channels are better than 10ppm, and the range of input current is increased to ±23mA, and other parameters such as zero and zero stability are improved comparing with the typical I/F convert. This paper provides a reference for the subsequent technical innovations of the I/F convert that are based on FPGA.