This research is based on the modeling of co-seismic deformations due to the fault movement in the elastic environments, and we can obtain the deformations generated in the faults. Here, modeling of the co-seismic displacement field is based on the analytical method with two spherical dislocation model and half-space dislocation model. The difference in displacement field from two spherical and half-space models, which is due to the spherical and flat view of the earth in two models has been investigated. Based on this modeling the sensitivity analysis of the difference between two spherical and semi-space models in the estimation of displacement field was compared to the geometric parameters of a simulated fault for a 100 kilometer longitudinal profile and we classified the effect of the fault parameters in the output results. According to the numerical results obtained from the sensitivity analysis are observed, the greatest effect of the slip rate parameter, followed by the depth of the fault, the dip angle, and the width and length of the fault parameters. These results mean that the greater the slip rate, depth, width, and length of the fault, or the Middle dip angle, the spherical model has better results than the semi-space model in the displacement field estimation.