Aim: This study used high performance liquid chromatography-tandem mass spectrometry to quantify the blood concentrations of 20 antidepressants, such as bupropion and fluoxetine, in human serum samples.Methods: After direct precipitation with a 1:9 protein precipitant of methanol and acetonitrile, serum samples were examined using high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS). The material was separated using a Poroshell 120 EC-C18 column (3.0mm×50mm, 2.7μm) and gradient elution. The mobile phases were phase A 0.01% formic acid aqueous solution (containing 2mmol/ml ammonium acetate) and phase B methanol solution. A 0.45ml/min flow rate was used to divide the sample and inject 5μl. Electrospray ionization source positive ion mode and multiple reaction monitoring modes were used for analysis. Measurement was quantified using an internal standard technique.Results: Accuracy ranged from 90.3 to 114.3%, intra-day precision from 100.1 to 112.3%, inter-day precision from 100.4 to 112.6%, extraction recoveries from 85.5 to 114.5% and matrix effect from 85.6 to 98.7%.Conclusion: This approach is fast, accurate, sensitive and repeatable. It can identify 20 antidepressants in blood simultaneously. This can be used to monitor blood drug levels and medication metabolism.