The junctions are prepared at the high composition end of nonlinear composition region and linear composition region respectively， and the photoelectric performance of HgCdTe detector with composition gradient was studied. By calculating the built-in electric field of composition gradient in two samples with different temperatures， the results show that the built-in electric field generated by the linear composition distribution is 100 ~ 200 V/cm， while the built-in electric field generated by the nonlinear composition distribution makes the electric field on surface of the sample as high as 2 000 V/cm. The analysis indicates that the influence of the built-in electric field generated by the composition gradient on the movement of the minority carrier is the main reason for the difference in the photoelectric properties of the two samples. By analyzing the three different trends of responsivity of the sample with different temperatures， it is proposed that using the built-in electric field generated by the composition gradient which is controlled by temperature can reduce the space charge effect and provides a new thought for improving the saturation threshold of the HgCdTe detector under large injection.