Abstract: In this study, the effect of gibberellin seed soaking on photosynthesis of maize has been studied, which provided a theoretical basis for the application of exogenous hormone on maize growth and seed processing. The seeds of maize (Zhengdan 958) were taken as experimental materials. 10, 60, 120 mg/L gibberellin (GA4+7) solutions were employed to soak and dry the seeds. The parameters of leaf photosynthesis and chlorophyll fluorescence, photosynthetic pigment content, leaf area and photosynthate accumulation were tested in the field. The results showed that priming the seeds with GA4+7 can improve the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, leaf area per plant, dry matter accumulation and photosynthetic pigment content and reduce the ratio of Chl a and Chl b, which effectively decreased the initial fluorescence (F0) and increased the maximal fluorescence (Fm), photochemical efficiency of PSⅡ(Fv/Fm) and quantum yield (⊿F/Fm'). Thus, it enhanced the hundred kernel weight and grain yield, and the most obvious effect was the sample treated with 60 mg/L GA4+7 (G2) among all these experiments results. In three-leaf stage, seven-leaf stage and jointing stage, compared with the control, the net photosynthetic rate of G2 significantly increased by 74.3%, 42.6% and 39.6% (P 0.05), respectively. The leaf area per plant significantly improved by 30.9%, 48. 5% and 24.1% (P 0.05), respectively. Moreover, dry matter accumulation sharply increased by 19.6%, 46.9% and 52.9% (P 0.05), respectively. The chlorophyll content was raised by 21.5%, 12.1% and 11.1% (P 0.05), respectively. As a result, the hundred kernel weight and the grain yield has increased by 6.0% and 9.7% (P 0.05), respectively.