Abstract: PVP-CdS modified gold electrode was prepared. Cyclic voltammetry was used to investigate the electrochemical behavior of tilmicosin at the modified electrode and differential-pulse stripping voltammetry was used for determination of tilmicosin. It was found that tilmicosin showed an oxidative peak at about 0.93 V in phosphate buffer solution of pH 7.50 when the scanning rate was 100 mV·s^-1 and the rest time was 10 s. Significant catalytic action toward electrochemical process of tilmicosin was observed at PVP-CdS modified gold electrode. Linear relationship between values of oxidation peak current at PVP-CdS modified gold electrode and mass concentration of tilmicosin was kept in the range of 0.5-300 mg·L^-1, with detection limit of 0.2 mg·L^-1. On the base of blank sample, test for recovery was made by standard addition method; values of recovery found were in the range of 93.0%-97.5%, with RSD's (n=5) in the range of 2.7%-4.1%.