In this paper,a design method of digital module for infrared focal plane readout circuit is introduced.In addition to the digital module including the line selection and column selection signals necessary for the readout circuit,only one control pin can be used to realize random windowing,upside readout,channel selection and the working mode selection,gain control,power consumption control and other functions of the readout circuit,and this single pin input design method can effectively avoid the noise and other aspects of the impact of excessive peripheral pins,and improve the stability and reliability of the large array readout circuit.The 0.18μmtechnology is adopted for the circuit,and the full custom design method is adopted with the array size of 1280×1024.The simulation results show that the circuit can realize the designed function normally,and is suitable for the large array infrared focal plane array.