Okadaic acid (OA) and dinophysistoxins 1 (DTX1) of diarrhetic shellfish poisoning (DSP) toxins were detected by ultra high performance liquid chromatography electrospray ionization tandem mass spectrometry(UHPLC MS/MS)．After the toxins being extracted using methanol and water(80∶〖KG-*3〗20, V/V)，the solution was further extracted with n hexane to remove lipid components and then cleaned up by solid phase extraction(SPE) on an C18 cartridge．The analytes were eluted with 50%（V/V）acetonitral water containing 0.2% formic acid on a Hypersil GOLD C18 column．The qualitative and quantitative determination of the toxins was performed by selective reaction monitoring (SRM) mode．OA and DTX1 were determined in the negative ion mode．The calibration curve was linear in the ranges of 25-400 μg/kg．The quantification limits of OA and DTX1were 5 μg/kg and 1 μg/kg, respectively．The mean recoveries at spiked concentrations of 5-100 μg/kg were more than 80% and the relative standard deviations were less than 10% (n = 6)．We studied toxin accumulation, transformation and elimination of DSP in 〖WTBX〗Meretrix meretrix〖WTBZ〗. The results showed that the increase in DSP content with the increase in time both in digestive gland and muscle during an 48 hour accumulation period when 〖WTBX〗Meretrix meretrixs〖WTBZ〗 were fed with 〖WTBX〗P. lima〖WTBZ〗. At the end of the accumulation period, the toxin amount of DTX1 in 〖WTBX〗Meretrix meretrix〖WTBZ〗 reached the regulatory limit in shellfish for OA group toxins. After the 96 hour elimination period, the amount of DSP decreased at least by 80%.