Photoprotection is an important strategy employed by plants to avoid photoinhibition under stress conditions. However, how photoprotection is regulated is not fully understood. Here, we show that exogenous calcium enhances the activity of cyclic electron flow (CEF) and non-photochemical quenching (NPQ) to regulate photoprotection in response to low night temperature (LNT) in pTRV2- PGR5 and PGR5-OE plants. A chloroplast calcium sensing receptor (CAS) protein was obtained by yeast two-hybrid and verified to interact with PGR5 via bimolecular fluorescence complementation (BiFC) and luciferase complementation imaging assays (LCA). Protein interaction analysis showed that PGR5 also interacts with PsbS. Interestingly, CAS promotes the interaction between PGR5 and PsbS, and the level of PGR5 and PsbS transcripts is reduced in cas mutants. NPQ is significantly reduced in psbs mutants, but this phenotype is attenuated after calcium application under LNT. Taken together, these results demonstrate that calcium signaling increases electrical signaling and energy dissipation efficiency under LNT conditions.