This manuscript is organized as following. First, I-V plots were generated using three methods under different ε0 and Γ, where we can observe the deviation of each equation from the other. We then compared ε0 and Γ extracted by fitting experimental results obtained from literature papers using the three Equations to evaluate the error level under different conditions. We certainly propose numerical recommended method in I-V analysis considering it adopts least theoretical approximation and showed the widest applicability, while the two methods (Eq 2 and Eq 3) have to be used under limited conditions. At last, we summarized a phase map of applicability of the three methods as a guide for their proper usage in charge transport study in molecular devices.