Abstract: The long duration of rainy weather in the Jianghan Plain leads to low light stress to wheat during the growing season. We examined the effects of shading at booting stage (S₁) and anthesis (S₂) on grain yield and physiological traits of two main wheat cultivars in Jianghan Plain, Zhengmai 9023 (ZM 9023) and Yangmai 23 (YM 23). 6-BA was sprayed before shading treatment (S₁+6-BA, S₂+6-BA) to explore the mitigation effect of low light stress by 6-BA. The results showed that 45% shading of full solar radiation at booting and anthesis stages significantly reduced grain yield, with greater effect at anthesis than that at the booting stage. Dry matter accumulation of grain during 14-21 days after anthesis was significantly decreased by shading. Shading at both growth stages reduced dry matter accumulation at maturity and changed the proportion of dry matter redistribution in vegetative organs. Consequently, grain yield was more dependent on the storage of photosynthetic assimilates of vegetative organs before anthesis, which resulted in a decline of grain yield in shading treatment. The grain yield of spraying 6-BA before anthesis was significantly greater than that of shading treatment, suggesting exogenous application of 6-BA could delay the senescence of flag leaf, grain filling rate and grain weight to mitigate the negative effect of shading. In addition, spraying 6-BA increased dry matter accumulation in the shading treatment at anthesis, and the translocation of post-anthesis assimilates. Grain weight of S₂+6-BA was higher than that with S₂, which ultimately increased grain yield as compared to the shading treatment. In conclusion, the negative impact of shading on wheat grain yield at anthesis was greater than that at booting stage. The application of exogenous 6-BA before shading at anthesis could mitigate yield loss of the shading treatment.