In this study, a solution for a liquid pool spreading model with a continuous spill is compared with that for a liquid pool spreading model with an instantaneous spill under the same total release volume. As reducing spill time in completely releasing liquid from a tank, it is evaluated whether the solution for a continuous spill approaches to that for an instantaneous spill or not. Also, effects of the viscous term in the liquid pool spreading model with continuous and instantaneous spills on the liquid pool spreading behavior are investigated.