In order to reduce the cost of silicon raw materials，thinner silicon wafers are used for crystalline silicon solar cells. Aluminum back-surface field passivation technique is more important for thinner solar cells PC1D method is used to model the aluminum back-surface field passivation technique of p-type monocrystalline silicon substrate 125×125 solar cells. The model results are analyzed. For a certain thickness solar cells，especially when the minority carrier diffusion length is greater than the thickness of silicon wafers，the back-surface recombination velocity is particularly important for efficiency. The efficiency will be increased with the increase of aluminum back-surface field junction depth，the decrease of back-surface recombination velocity and the increase of minority carrier lifetime. Aluminum back-surface field can improve the quality of the back-surface passivation，reduce the back-surface recombination velocity thus improve the efficiency of solar cells，which is commonly used for the commercial crystalline silicon solar cells.