Most of mid-wave and long-wave infrared detectors for space application operate against high background. For a linear HgCdTe infrared detector array, because of the large dark current of itself and the serious nonuniformity of dark current in each of its detection elements, the dynamic range of its output signal is too small and even the signal voltage of part detection elements can not be read out when the conventional readout circuit is used. A readout circuit which has an element-by-element background suppression function is designed for a linear mid-wave infrared detector array. It is designed by combining voltage-current conversion with current storage. This method not only can suppress the dark current from different detection elements, but also can effectively improve the signal-to-noise (SNR) of the circuit and increase the dynamic range of the output signal. The test result show that the circuit has its output swing of 2 V at the low temperature of 90 K and the nonuniformity of its output voltage is reduced by 70%. Therefore, this research is of significance to the engineering design of mid-wave and long-wave infrared detectors.