This paper compares the direct theory-Green's theory, and indirect method-potential theory, which aims at transiting the partial DE into the boundary IE for the harmonic transformation model. Comparing with the Green's theorem, potential theory is simple and easy to implement. By detecting the singularity point in the harmonic model, potential theory has been verified that it is more efficient. Experimental results illustrate that the indirect method applied for the harmonic transformation model has good performance comparing with the direct method.