In order to fully utilize the limited space and field of view in deep space exploration， a camera with three linear TDI CCD detectors is proposed. To acquire remote sensing images with high SNR and high-resolution， according to the chain of the imaging system， methods for analyzing the key factors that affect the SNR of high-resolution cameras as well as improvement measures are put forward. First， each channel is designed independently to reduce circuit coupling between channels. Then， the time-constant of the vertical transfer frequency is adjusted to reduce the crosstalk of the inner TDI CCD. Finally， the three detectors are physically isolated to reduce the near field coupling noise. The results of the radiation calibration experiment with the high-resolution camera in Tianwen-1 indicate that by simulating the orbital conditions of Mars， the SNR of the panchromatic spectrum is 115.1 when the integral number is 32， as the elevation angle of the sun is 30° and the surface albedo is 0.2. The results show that the design satisfies the criteria for Mars exploration.