Abstract： ObjectiveTo improve the key technology of immunesensors in immobilizing biosensitive element and keeping its hioactivity, an enzyme immunosensor based on chitosan-SiO_2 ( CS-Sio_2 )hybrid membrane was fabricated. To estimate the new immunosensor Vibrio parahaemolyticus which was the main pathogens of aquatic products. MethodsA CS-SiO_2 hybrid membrane was prepared using sol-gel method. The enzyme immunosensor was fabricated by coating the membrane and horeseradish peroxidase labeled Vibrio parahaemolyticus antibody (HRP-anti-VP) on the surface of four-channel screen-printed carbon electrode. The immunosensor was characterized by cyclic voltammetry. Vibrio parahaemolyticus could be detected according to the decrease percentage (DP) of peak current before and after immune response,while cyclic voltammetry was used as an electrochemical mean to detect the products of the enzymatic reaction. Seven kinds of bacteria, like Vibrio alginolyticus, were selected for specific experiments. Results By studying the infrared spectrum of three kinds of films, the CS-SiO_2 hybrid membrane was prepared and HRP-anti-VP was fixed in the hybrid membrane. Under the optimum conditions of immunoreactian and electrochemical detection,the DP of peak current before and after immune response showed a linear relation with lgC in the range of 10~4 - 10~9 cfu/ml,while the linear regression equation was: DP =6. 5 lgC -3. 319,the correlation coefficient was 0. 9958 and the detection limit was 6. 9 × 10~3 cfu/ml ( S/N = 3 ). The immunosensor possessed acceptable specificity, reproducibility ( RSD < 6% ), stability ( the amperometric response was 95% of the initial response after a week) and accuracy (96. 7% of the results obtained by the immunosensor were in agreement with those obtained by GB/T 4789. 7-2003 ). ConclusionThe enzyme immunosensor based on CS-SiO_2 hybrid membrane gave a good performance in rapid detection of Vibrio parahaemolyticus.