The homeostasis of the proline-Δ-pyrroline-5-carboxylate (Pro-P5C) cycle, mediated by proline dehydrogenase (ProDH), plays a critical role in plants in response to abiotic stresses. The biological function of gene under drought stress and its effects on amino acid metabolism and photosynthesis through proline metabolism were investigated. Enzymatic characterization of the CsProDH1 protein was conducted in vitro. Overexpression of aggravated plant stress, as evident by reduced photosynthetic efficiency and increased reactive oxygen species, which activated the Pro-P5C cycle. In contrast, silencing enhanced plant drought resistance, increased proline accumulation, and protected photosynthesis. Studies indicate that exogenous amino acid application mitigates drought-induced physiological impairments in plants by maintaining cellular homeostasis, with particular efficacy observed in enhancing tea plant drought resilience through improved osmotic adjustment and antioxidant capacity. This study uncovers the significant role of in plant drought resistance and its regulatory mechanism, offering potential gene targets and application strategies for enhancing crop drought resistance.