Polypyrrole was synthesized on the surface of expanded graphite by potentiostatic electrodeposition.The imino group of polypyrrole combined with glutaraldehyde by crosslink to form a stable interface of expanded graphite/polypyrrole/glutaraldehyde.When human the IgG antibodies were immobilized onto the interface with glutaraldehyde as a cross linker，a novel electrochemical immonusensor was fabricated.The detection of human IgG is based on the principle of “sandwich” immunoassay.After the sensor was incubated in the solution containing IgG，the IgG fixed on the sensor surface combined with the HRP-labeled IgG second antibodies and the IgG antibodies to generate ternary immunocomplexes.HRP of the immunocomplexes can be used to catalyze the reduction of H2O2 and the determination of IgG can be realized by measuring the reduction current of H2O2.The experimental factors，including incubation temperature，incubation time，pH value and H2O2 concentration were investigated.Under the optimal conditions，the calibration curve was linear in the range of 1-50 mg?L-1 with a detection limit（S/N=3） of 3.5 μg?L-1 .This novel electrochemical immunosensor showed a high accuracy.The inter- and intra-groups relative standard deviations（RSDs） of this immunosensor for IgG determination were 2.4% and 4.0%，respectively.The electrochemical immunosensor was applied in the determination of IgG concentration in two real serum samples，with IgG concentrations of 9.60 g?L-1 and 9.28 g?L-1,respectively.The recoveries for both samples were 105%.With the advantages of simplicity，repeatability and low cost，the electrochemical immunosensor based on expanded graphite substrate is feasible to develop into a disposable electrochemical sensor for immunological test.