Wheat is the main food crop in the north of China, so its yield level is closely related to people's living standard and the national food security. Wheat plants often suffer cross-stress of heat and high light during grain-filling stage in the area, which leads to damages in photosynthetic apparatus, early decline of photosynthesis and finally reduction of grain yield. Therefore, much attention is currently being paid to the effect of heat and high light stress on the photosynthesis of wheat plants during grain-filling period. In photosynthesis system of plants, the reaction center in photosystem Ⅱ (PS Ⅱ) is the key site vulnerable to multiple stresses such as heat, drought and high light; moreover, the extent of its damage depends on the balance between injury and repair. The repair of PSⅡ requires efficient turnover of D1 protein, which is the key component of PSⅡ. During the repair of PSⅡ, damaged D1 protein must be degraded and replaced by a new copy quickly. It has been known that Deg5 protease plays an important role in cleavage of damaged D1 protein. However, the changes of Deg5 protease under heat and high light stress are still not known. Salicylic acid (SA) is a phenolic substance which has been used as a plant hormone for a long time. A lot of recent reports have shown that SA plays an important role in response to abiotic stress in plants. In this study, the wheat cultivar "Aikang 58" was used to investigate the effects of SA on Deg5 protease, D1 protein and PSⅡ performance under heat and high light stress. Wheat leaves at grain-filling stage were pretreated with 0.1 mmol/L SA and water (as control), respectively and then subjected to different temperature and light treatments: moderate temperature and light (25℃, 600umol m^-2 s^-1, MTL) for 2h, high temperature and light(38℃, 1600 μ mol m^-2 S^-1, HTL)for 2h, and recovery for 3h under MTL after 2h of HTL. Fluorescence parameters were measured using a chlorophyll fluorometer and the changes of Deg5 protease and D1 protein contents were analyzed by western-blotting. The results showed that heat and high light stress resulted in decreases of Deg5 protease, D1 protein and F_v/F_m (maximal photochemical efficiency of PSⅡ) and an increase of F_o (chlorophyll initial fluorescence). Compared with the control, pretreatment with SA increased the levels of Deg5 protease, D1 protein and F_v/F_m and decreased F_o. It was suggested that exogenous SA could alleviate the damage to Deg5 protease and D1 protein and maintain PSⅡfunction of wheat chloroplasts under heat and high light stress.