In order to meet the demands of space imaging with high resolution and large dynamic range at low light level (LLL), digital domain time delay and integration (TDI) technology based on scientific complementary metal-oxide-semiconductor (sCMOS) image sensor with global shutter is proposed, and image data processing algorithm is deduced. Corresponding signal-to-noise ratio (SNR) model is established, dynamic range extension imaging method based on digital domain TDI is proposed, and modulation transfer function degradation due to velocity errors is analyzed. Experimental results show that the proposed method can significantly improve LLL image quality. System's SNR increases from 5.04 dB to 19.78 dB with 30 TDI stages, and dynamic range increases by 29.54 dB compared to traditional digital domain TDI method, which highlights the potential of the proposed method for space LLL imaging with high resolution and large dynamic range.