Famotidine is a histamine H2 receptor antagonist, which has a significant inhibitory effect on gastric acid secretion. The quenching effect between famotidine and bovine serum albumin (BSA) is studied with the analysis of fluorescence spectrum and ultraviolet visible absorption spectrum, and the interaction mechanism between them is elucidated. The results show that famotidine has strong quenching effect on the endogenous fluorescence of BSA, and the quenching mechanism is static quenching. The apparent binding constant KA of famotidine and BSA at 306 K and 314 K is determined to be 9.861×10 4 L/mol and 3.891×10 4 L/mol. The calculated thermodynamic parameters show that the interaction between famotidine and BSA is mainly hydrogen bond and van der Waals force. According to the F rster nonradiative energy transfer theory, the interaction distance of famotidine and BSA is calculated to be 1.25 nm, and nonradiative energy transfer occurs.