Electron Multiplying Charge Coupled Device(EMCCD) can realize read out noise of less than 1e- by promoting gain of charges with the charge multiplication principle and is suitable for low light imaging. With the development of back illuminated CMOS technology CMOS with high quantum efficiency and less than 1.5e- read noise has been developed by Changchun Institute of Optics, Fine Mechanics and Physics(CIOMP). Spaceborne low light detection cameras based on EMCCD CCD201 and based on CMOS were respectively established and system noise models were founded. Low light detection performance as well as principle of spaceborne camera based on EMCCD and spaceborne camera based on CMOS were compared and analyzed. Results of analysis indicate that signal to noise(SNR) of spaceborne low light detection camera based on EMCCD will be 23.78 as radiance at entrance pupil of the camera is as low as 10-9 W·cm-2·sr-1·μm-1 at the focal plane temperature of 20 ℃. Spaceborne low light detection camera worked in starring mode and the integration time is 2 s. SNR of low light detection camera based on CMOS will be 27.42 under the same conditions. If cooling systems are used and the temperature is lowered from 20 ℃ to -20 ℃, SNR of low light detection camera based on EMCCD will be improved to 27.533 while SNR of low light detection camera based on CMOS will be improved to 27.79.