With the development of uncooled infrared focal plane array technology,the design of infrared readout circuit becomes more and more important. A readout circuit of infrared focal plane unit with suppression of the background current was designed. Based on the first generation of SI circuit,the readout circuit was improved and realized the suppression of the background current. The overall architecture and working principle of the system circuit are explained in detail,and the circuit was simulated by Spectre software. Results show that the scheme can suppress background current and realize infrared readout function.