The main factors which influence the compound between the passivation medium layer and the crystalline silicon are analyzed, including the interface state density(Dit), surface charge density of medium lay. er, doping type and doping concentration of the substrate. When the carrier injection level varies, the passivation quality is closely related to the charge type in medium layer and silicon doping type. As the carrier injection level decreases, the passivation quality of the passivation medium with positive charge on the P-type(N-type)sili. con decreases, but the passivation quality of the passivation medium with negtive charge on the P-type(N-type)silicon still remains constant. The reason of the passivation quality varying with carriers injection level is analyzed. The guiding suggestion for the high effiency crystalline silicon cells is proposed, it is very important for silicon cells operating at low level injection level(5×1014 cm-3).