To explore the role of receptor-like kinases in the regulation of photosynthesis, an uncharacterized TaRKL1 encoding a receptor-like cytoplasmic kinase was investigated in Triticum aestivum cv. Xiaoyan 101 with Barley stripe mosaic virusinduced gene silencing system (BSMV-VIGS). The results showed that the CO2 assimilation rate, stomatal conductance, and transpiration rate were significantly lower in the BSMV:TaRKL1 plants than those in the BSMV:γ00 plants (control). Moreover, the maximum photochemical efficiency and electron transport flux decreased while the dissipated energy flux was enhanced in the BSMV:TaRKL1 plants compared to the control. Additionally, the contents of chlorophylls and carotenoids were reduced in the BSMV:TaRKL1 plants. However, the hydrogen peroxide content was significantly enhanced in the BSMV:TaRKL1 plants, which resulted from lower ascorbate peroxidase activity. Consistent with the inhibition of photosynthesis, the transcription levels of the photosynthesis-related, antioxidant enzymes, senescence-associated genes, and four abscisic acid biosynthesis genes were downregulated substantially. Collectively, this study for the first time showed that TaRKL1 regulates photosynthesis and H2O2 homeostasis. It may be a potential target gene for radiation-use efficiency improvement in wheat.