After giving a theoretical explanation of the feasibility of the conversion of apparent complex resistivity amplitude spectra into apparent phase spectra, this paper, in combination with the practical situation, deals with the error propagation in the process of this conversion. It is concluded that such a conversion, though theoretically feasible, is generally infeasible in practice. The implication of this conclusion lies in the fact that in general the apparent phase spectrum data can only be collected in practice .although this will lower the efficiency of field work.