The inhibition of aldose reductase is an effective strategy to alleviate symptoms of diabetic complications. The p‐coumaric acid ethyl ester (p‐CAEE) was taken as an example to investigate the inhibition of aldose reductase from p‐coumaric acid derivations. The results showed p‐CAEE strongly inhibited aldose reductase with the half inhibitory concentration of 1.92 μM, following the noncompetitive manner with a Ki value of 0.94 μM. After binding with p‐CAEE, the enzyme showed increased β‐sheet content, and the α‐helix content, random coil content, and intrinsic fluorescence strength decreased. p‐CAEE bonded with aldose reductase at the anionic, hydrophobic, and selective pockets of the enzyme, via hydrogen bond and hydrophobic interactions with Thr113, Cys80, Trp111, and Leu300, etc. The strong inhibition was related to the high oil–water partition coefficient and special esterify group. This study provides new information to develop aldose reductase inhibitors from p‐coumaric acid derivations. Practical applications Inhibition of aldose reductase is an effective strategy to alleviate and control the symptoms of diabetic complications. In this study, it has been shown that p‐coumaric acid ethyl ester could strongly inhibit the aldose reductase. In addition, the inhibition of aldose reductase was been correlated with structures and oil–water partition coefficients of p‐coumaric acid derivatives. It provides a theoretical basis for the development of effective aldose reductase inhibitors.