Objective The diarrhetic shellfish poison (DSP) was investigated in shellfish samples collected from Feb 2011 to Jan 2012 in Tianjin seafood market. Methods Mouse bioassay and LC/MS-MS method were used to determine toxin content and its component. Results DSP was detected only in samples of scapharca subcrenata collected on May and august from TangShan, and both were over the limit. DTX-1 and YTX were confirmed in the positive samples by LC/MS-MS. Conclusion The overall DSP detection rate in shellfish from Tianjin market was low, but still essential to prevent the risk in spring and enhance monitoring and public education in summer.