An ultra high performance liquid chromatography-tandem mass spectrometric method (UHPLC-MS/MS) was developed for the simultaneous determination of three natural forms of azaspiracids (AZA-1, AZA-2 and AZA-3) in edible shellfishes such as mussels, oysters, clams and scallops. The samples were homogeneously extracted with acetonitrile-water (85: 15, v/v). The resultant supernatants were purified with QuEChERS method and filtrated by 0.2 microm microporous filters. The separation was performed on an Agilent ZORBAX Eclipse Plus C18 column (100 mm x 2.1 mm, 1.8 microm) with the gradient elution using acetonitrile/water (containing 5 mmol/L ammonium acetate and 0.1% formic acid) as mobile phases. The three azaspiracids were detected using positive electrospray ionization (ESI +) followed with multiple reaction monitoring (MRM), and quantified by external standard calibration method. The calibration curves showed good linearity in the range of 1-100 microg/kg with the correlation coefficients (r2) greater than 0.995. The limits of quantification (LOQ, S/N = 10) were 1.0 microg/kg for all the three AZAs. The average recoveries of azaspiracids spiked in the matrix at the levels of 10, 20 and 50 microg/kg ranged from 71% to 108%. The relative standard deviations (RSDs) of inter-day and intra-day determinations were less than 10% (n = 6). The samples from several areas within and outside of China were screened, and some of the samples showed positive for azaspiracids. The developed method is easy to operate, very reproducible, sensitive, and efficient. It can be applied to the determination of the three forms of AZAs in the edible shellfishes as well shellfish products.