In order to improve performance of CCD(charge coupled device) at low light levels, a new technique of eliminating readout noise is presented after analyzing the short of classical technique, namely, correlated double sampling.First, the primary kinds of noise in CCD are analyzed, and then a platform for generating and analyzing the noise in CCD is established. An array of proper numbers can be found to be used in the practical filter circuit from the result obtained by the platform under low light level. Therefore, the reset noise of CCD can be eliminated more efficiently than classical technique and any other noise passes doesn’t introduced through digital filter.