Several numerical tests have been analyzed in this paper to discuss the influences from the uncertain parameters of the presumed inversion fault model. The influence from the data to the resolution of the inversion results has been also analyzed. We have discussed the influence from the time length of the data and distribution of observational stations. Our research indicates: (1) The near-field waveform data can well reveal the source rupture process of the shallow part of the fault, however, it poorly constrains the slip distribution on the deep part of the fault. Jointly using near- and far-field waveform data can provide more complete message on the rupture process of the whole fault. (2) The near-field inversion result on the source is very sensitive to the strike and dip parameters of the presumed fault model. 2° deviation for the presumed strike and 5° deviation for the presumed dip angle from that of the true fault will lead to a distorted inversion result. (3) The influence from the uncertain media structure for Chi Chi earthquake faulting process inversion might be ignored if we can take the difference between Ma's model and Wu's model as the measure of the media uncertainty.