Abstract: To get better insight into the photosynthetic mechanism of plant adaptation to strong light in intercropped maize, a field trial was carried out in 2014-2015 to investigate the effects of maize/peanut intercropping row ratio and phosphate fertilizer on diurnal variation in light intensity of maize canopy, SPAD value, and the curves of photosynthetic response of net photosynthetic rate (P_n) to photon flux density (PFD) and to CO₂ of functional leaves. The field trial comprised 2 rows maize intercropped with 2 rows peanut (2:2, R₁), 2 rows maize intercropped with 4 rows peanut (2:4, R₂) and 2 rows maize intercropped with 8 rows peanut (2:8, R₃). Results showed that the light intensity of intercropped maize canopy was R₃>R₂>R₁. From pre-tasselling to filling stage, the SPAD value, apparent quantum efficiency (AQY), light compensation point (LCP), light saturation point (LSP), maximum net photosynthetic rate, carboxylation efficiency (CE), maximum electron transfer rate (J_max), triose phosphate utilization (TPU), stomatal conductance (g_s), transpiration rate (T_r) and P_n in ear leaves of intercropped maize were R₃>R₂>R₁, but the intercellular CO₂ concentration (C_i) was R₁>R₂>R₃. At dough stage, the AQY, LSP_n, g_s, CE, J_max and TPU in ear lea-ves of intercropped maize in R₃ intercropping system were lower than those in R₂ intercropping system. The photosynthetic indices, such as AQY, LSP_n, CE, V_{c max}, J_max and TPU were increased by phosphate fertilizer application. These results suggested that the key mechanisms that enhanced strong light utilization ability of intercropped maize were attributed to gradual improvement in g_s, AQY, CE, V_{c max}, J_max and TPU of ear leaves with increasing light intensity, however, beyond a certain light intensity, intercropped maize leaves were prone to premature senescence. Nonetheless, phosphate fertilizer could improve light utilization and delay leaf senescence in intercropped maize.