The effects of arbuscular mycorrhizal fungi (AMF) on the photosynthetic characteristics of melon under low light and salt stress were investigated by pot experiment in greenhouse. It follows that AMF significantly increased chlorophyll content, net photosynthetic rate (Pn), photosynthetic electron transport rate (ETR), water use efficiency (WUE) and stomatal limitation factor (L_s) in melon seedlings under low light and salt stress. Stomatal conductance (G_s), transpiration rate (T_r) and intercellular CO₂ concentration (C_i) also increased with the prolongation of stress time. The changes of photochemical quenching coefficient (qP) and actual photochemical efficiency (Φ_PSⅡ) were significantly higher than those of inoculation (A_max), light saturation point (LSP) and apparent quantum efficiency (AQE) significantly increased (P <0.05), and the maximum photochemical efficiency (F_v/F_m) was significantly enhanced by inoculation with AMF, but the difference was not significant, while light compensation point (LCP) and dark respiration rate (R_d) reduced. We propose that AM symbiosis can protect melon plants from low light and salt stress by improving their chlorophyll fluorescence, gas exchange parameters and light response parameters.