Abstract: In order to effectively read the nuclear pulse signal of coplanar-grid CdZnTe (CPG-CZT) detector, a readout circuit that can be used for CPG-CZT detector based on CPG-CZT detector measurement principle and domestic and foreign research was designed in this paper. The circuit mainly includes high voltage bias circuit, preamplifier circuit, gain adjustment and subtraction circuit. For studying the performance of the readout circuit, the performance of each unit circuit was test. Besides, the variation law of the energy resolution of detection system with the bias voltage and the relative gain G of the two signals in the gain adjustment circuit was test. The results show that the R² between the two-output bias voltage of the high voltage bias circuit and the input bias voltage is as high as 0.998, the output noise of the preamplifier circuit is 5 mV, and the output signal noise of gain adjustment and subtraction circuit is 10 mV. The changes of the input bias voltage and the relative gain G will affect the detection system energy resolution. When the bias voltage is -1 650 V and the relative gain G is 0.7, the detection system has the best energy resolution of 3.65% for γ-ray generated by ¹³⁷Cs source and there is no obvious tailing phenomenon.