The invention generally relates to the field of CMOS (Complementary Metal-Oxide-Semiconductor) image sensors, in particular to a method for inhibiting electrical mutual interference of a backside illuminated CMOS image sensor. According to the method, two ion implantation layers are implanted into different regions of the back surface of a pixel unit by the CMOS image sensor after back surface thinning, ion concentrations of the two ion implantation layers are simultaneously controlled to be reduced from the top down, and an electric field pointing from the top down is formed in an epitaxial layer, can absorb electrons generated due to the fact that incident light arrives at a substrate region outside a space charge region of a photosensitive diode, and reduces diffusion of the electrons among different pixels in a substrate, so that the electrical mutual interference among the pixels due to the diffused electrons can be reduced; a production technology is improved; and the image quality of the CMOS image sensor is improved.