We developed a numerical method for PFI engine, which would take complex intake-port phenomena into consideration. Numerical study for PFI engine has additional difficulty compared with that for GDI engine, because in-cylinder distribution of mixture is strongly affected by remaining fuel in intake-port. The new simulation method proposed in this paper has adopted split calculation of two steps. Fuel distribution in intake-port is calculated in the first step, and then this result of adhered and floating fuel distribution in intake-port is used as boundary and initial conditions in the next step. Together these two steps realize accurate in-cylinder mixture distribution prediction. According to experimental verification, the new method showed a capability to predict accurate liquid film distribution with less calculation cost. And then we applied the method into the investigation for optimum injection strategy to improve engine performance and to reduce emission. Finally we confirmed the method works effectively for PFI engine simulation.