Abstract: A method was developed for the determination of nodularin (NOD) in algae-based health food by ultra-performance liquid chromatography-triple quadrupole tandem mass spectrometry (UPLC-MS/MS). The analytes were extracted from algae-based health food powder with methanol/water (80:20, v/v), and purified before analysis. The separation of analytes was performed on an Agilent Infinity Poroshell 120 SB-C₁₈ chromatographic column (2.1 mm×100 mm, 2.7 μm) with the gradient elution of acetonitrile and water (containing 0.01% formic acid) as mobile phases. Qualitative analysis was performed by multiple reaction monitoring (MRM) mode. Matrix matched standard curve was used for quantitative analysis. The chromatographic and MS parameters were optimized. Major factors affecting the extraction and clean-up efficiencies including the type of extraction solvent and clean-up cartridges were investigated. The nodularin had a good linear relationship in range of 0.5~50 μg/L and correlation coefficient (r) was 0.9997. The limit of detection (LOD, S/N=3) and limit of quantification (LOQ, S/N=10) were 1 and 3 μg/kg, respectively. The spiked recoveries of nodularin at 3 spiked levels were 103.6%~114.8%, and relative standard deviations (RSD) were 3.3%~12.5% (n=6). The established method was simple, rapid and quantitatively accurate, which was suitable for quick analysis of nodularin in algae-based health food.