In order to improve the image quality of the time delay integration complementary metal oxide semiconductor (TDI CMOS) image sensor, the influence of integration time selected on image quality is studied. Based on the rolling shutter readout principle, the impacts of integration time on signal to noise ratio (SNR) and modulation transfer function (MTF) are analyzed respectively. According to the results of the analysis, it is proposed that in the case of series selected，the optimal value exists in the selection of integration time, which makes a better image quality. To validate the conclusion, on the basis of self-developed TDI CMOS image sensor chip and field programmable gate array (FPGA) development board, the imaging testing system of TDI CMOS image sensor is set up. By using MTF × SNR as the image quality evaluating index in the experiment, the experimental results show that under the selected camera parameters, the stage is 8, and the light intensity is 20 lx, when the integration time is 64 ms, the best image quality can be obtained and the MTF× SNR is maximum.