To detect exoplanets and study their formation and evolution, several exoplanet space missions, such as Kepler, TESS, GAIA, and CHEOPS, have been successfully developed and fully operated in space. However, China has not yet had its own exoplanet space mission. The Earth 2.0 (ET) space mission is being developed in China aiming at detecting and characterizing exoplanets, especially extra-terrestrial like planets. ET will carry six transit telescopes pointing to the same sky region and a gravitational microlensing telescope, with the goal of finding habitable Earth like planets (Earth 2.0s) around solar type stars and measure its occurrence rate. In order to detect Earth 2.0s, ultrahigh-precision photometry of ∼30 ppm is required, which places tight constrain on camera performance, such as high-speed readout, low readout noise, mosaic detectors, and radiation tolerance. As of now, a prototype camera utilizing a CCD250-82 detector from Teledyne e2v has been developed and its performance has been tested. At a readout rate of 2 M pixels/s, the readout noise of 10.96 e− RMS and the pixel response nonuniformity of 0.66% at 600 nm have been achieved. After receiving radiation doses of 5 krad (Si) and 13.43 krad (Si), the dark current of the CCD increased by 30% and 126%, respectively. The camera’s key performance meets the basic requirements for the ET space mission, except for its high cooling power consumption.