The relative error formula of the Cagniard resistivity was calculated so as to know the influence of the the location of the antenna laid in CSAMT on the Cagniard resistivity, which was based on the wave zone of the electromagnetic fields in the homogeneous half-space ground caused by the horizontal electric dipole source. In the case of given parameter, three models of the antenna deviations, i.e., horizontal deviation, vertical deviation and comprehensive deviation, were built, and the characteristics of the influence of each model on Cagniard resistivity were discussed. The maximum relative errors of these models on Cagniard resistivity are 170%, 7% and 190% respectively. In addition, the influence of the antenna horizontal deviation of the antenna on Cagniard resistivity is more obvious than that of the vertical deviation.