Wetting balance test is known to be the most versatile method to evaluate wettability during soldering process, because it provides quantitative information and time dependent wetting behavior. There are many other studies exist related with the wetting force, however, as to wetting time, there are few theoretical backgrounds and mathematical analysis. In this study, the wetting time is focused on a wettability index. The wetting curve, which shows time dependant wetting behavior, is predicted by using computer simulation and compared with oil experiment also, the mechanism of meniscus rise is analyzed. As a result, relationship of calculated and measured wetting curve can be obtained. It is found that the viscosity of a liquid is the major variable that determine the wetting time and wetting rate.