Under low phosphorus stress, the benefits of Si application on improving Si accumulation, P accumulation and chlorophyll fluorescence parameters of maize during seedling stage were investigated using medium ZH2 and ZH115 by sand culture experiment. The treatments consisted of three P levels (0.01 mmol/L, 0.1 mmol/L and 1 mmol/L) and three Si (0 mmol/L, 0.75 mmol/L and 1.5 mmol/L). Maize seedlings were incubated for 28 days, then the items were measured, including chlorophyll fluorescence parameters of the first top fully expanded leaf, dry matter accumulation, Si content and accumulation, P content and accumulation. The main results were as follows: (1)The dry matter accumulation, Si and P accumulation amount of these two varieties (ZH2 and ZH115) reduced by 34.73% and 39.26%, 29.10% and 33.01%, 81.81% and 87.63% in average, meanwhile the open degree of PSⅡ reaction center, efficiency of lightcapture, efficiency of light energy transformation and electron transportation of the leaf all decreased significantly, and heat dissipation of the leaf also increased with P concentration from P3 to P2 and P1 in culture medium. (2)The dry matter accumulation, Si and P accumulation amount of these two varieties (ZH2 and ZH115) increased by 21.54% and 36.05%, 120.08% and 236.65%, 39.81% and 69.17% in average, meanwhile the open degree of PSⅡ reaction center, efficiency of lightcapture, efficiency of light energy transformation and electron transportation of leaf also increased significantly with Si concentration from Si1 to Si2 and Si3 in culture medium. (3)There were significantly positive correlation between P accumulation and Si accumulation in plant. Fv/Fm (XE), Fv′/Fm′ (XE′), Fq′/Fm′ (φPSⅡ), and ETR showed significantly positive correlation with P accumulation in plant, and the same with Si accumulation. When P concentration in culture medium was 1 mmol/L or 0.1 mmol/L, comparing to treatment of Si1, dry matter accumulation, Si accumulation, P accumulation, efficiency of light energy transformation and electron transportation of ZH2 and ZH115 all increased under the treatment of Si2 and Si3; but the treatment of Si2 and Si3 on improving above items was very weak when P concentration in culture medium was 0.01 mmol/L. In summary, the improvements in phosphorus deficiency tolerance of maize were resulted from increasing Si and P uptake and accumulation in plant, efficiency of light energy transformation and electron transportation of leaf, and decreasing in photo inhibition by Si application, even these benefit of it could be found more under normal P level.