PURPOSE: A detection method of sertraline in blood plasma is provided, thereby rapidly and accurately detecting sertraline in blood plasma. CONSTITUTION: A detection method of sertraline in blood plasma comprises the steps of: removing proteins from animal blood plasma; regulating pH of the protein-removed blood plasma to 11.5 to 12.5; extracting the pH-regulated blood plasma with a nonpolar solvent; and measuring the concentration of the extracted sertraline using gas chromatography/mass spectrometer, wherein the nonpolar solvent is diethylether; and the pH regulation is carried out by using Na2HPO4-NaOH.