SLM is the method that has triumphed theoretical I-V studies as powerful and valuable analyzing methods in exploring tunneling transport in molecular junction. The theoretical modeling of I-V is promising to understand energy level in charge transport at the molecular junction, which also relies crucially on our proficiency of utilizing these modeling methods. However, the applicability and accuracy of using these models have not been well evaluated. Indeed, different single level mathematical methods also rendered significant variation in extracted transport parameters. We thus developed the interest of detailed examination of condition and limitation of their application in modeling I-V response of the junction. This work provides extensive study on SLM methods, including the numerical integration of Landauer formula (Eq 1), and other two analytical tunneling models, Eq 2 and Eq 3, believing that the main problem is on appropriate condition in using each tunneling models in examining molecular structure. Our work will clarify the conditions and limitations inherited in I-V analysis using these methods and provide a proper guide for the modeling methods.