This paper mainly studies the preparation process of N-type high-efficient crystalline silicon tunnel oxide passivated contact (TOPCon) cells by low pressure chemical vapor deposition (LPCVD) method. The influencing factors of the preparation of tunnel oxide layer and polycrystalline silicon layer by LPCVD were studied and analyzed. The effects of different oxide layer thickness, polysilicon thickness and polysilicon doping amount on the efficiency were studied. The results show that: the thickness of tunneling oxide layer of 1.55 nm shows the best passivation effect; the Voc reaches the highest value when the thickness of polysilicon layer is 120 nm; the Eff reaches the highest when the thickness of polysilicon layer is 90 nm. The field passivation effect of polysilicon layer increases with the increase of P doping concentration. Higher Voc can be obtained when the P doping concentration is 3.0×1015 cm-2.