4-Ethyl-2-methoxyphenol is a widely used food additive, but it also has toxicity. In order to investigate the effect of 4-Ethyl-2-methoxyphenol on the body, the interaction between 4-Ethyl-2-methoxyphenol and human serum albumin (HSA) was studied by combining a variety of spectroscopic techniques and molecular simulation techniques in this paper. UV absorption spectra results indicated that 4-Ethyl-2-methoxyphenol formed a new complex with human serum albumin. In addition, the fluorescence spectra results showed that the presence of 4-Ethyl-2-methoxyphenol can enhance the fluorescence intensity of HSA. 15 nm synchronous fluorescence and fluorescence enhancement effect equations can be used to calculate the binding constants between 4-Ethyl-2-methoxyphenol and HSA, and their binding constants decreased with the increasing of temperature. Thermodynamic parameters showed that 4-Ethyl-2-methoxyphenol was mainly bonded with HSA by hydrogen bonding and hydrophobic interaction. Moreover, synchronous fluorescence, three-dimensional fluorescence and circular spectra revealed that 4-Ethyl-2-methoxyphenol modified the conformation of HSA. The molecular docking technique demonstrated that 4-Ethyl-2-methoxyphenol was bonded in the IB hydrophobic region of HSA.