Objective To analyze the characteristics of major allergen components from protein extracts of swimming crab Portunus trituberculatus in Tianjin region.Methods Crude protein extracts were prepared from the crab and separated by SDS-PAGE,then transferred to PVDF membrane and incubated with patients’ specific IgE(sIgE) serum mixture and individual patient’s sIgE serum,respectively.After incubated with the second antibody,the reactivity was detected among different patients.Results SDS-PAGE showed 9 protein bands in the extracts,of which 70 and 74kD were at high level.Western blot showed that patients’ sIgE serum mixture could react with the majority of proteins in the extracts except 21 and 38kD proteins.The allergens in different patients were heterogeneous.Conclusion Three major allergens(36,48 and 94kD protein) were identified in the extracts of swimming crab Portunus trituberculatus from Tianjin,but there was also individual difference.