A highly sensitive label free electrochemical immunosensor was developed for the determination of human IgG based on a gold electrode modified with GNPs and carbon nanotubes（CNTs） incorporated with chitosan composite and the IgG antibody was directly absorbed on the modified electrode surface. The electrochemical behaviors of the modified electrode were investigated by cyclic voltammetry（CV）and AC impedance.The influence of electrolyte pH on immunosensor was studied by differential pulse voltammetry（DPV）. A good linearity was obtained between response current and concentration of human IgG antigen in the range of 0.05-455 μg/L，with a correlation coefficient(r2) of 0.991 1. The detection limit（S/N=3） was 0.01 μg/L. Compared with the traditional methods，the immunosensor exhibited the advantages of simple preparation，high sensitivity and long-term stability without any consumption of reagent for signal amplification.