We have developed a new scheme for the simulation of port fuel injection (PFI) gasoline engine, in which intake-port phenomena can be considered and low computation cost is promised. The simulation for PFI engine is difficult because intake-port phenomena should be predicted. One conventional method to simulate PFI engine is to simulate the whole cylinder and intake port with many engine cycles, then a steady mixture distribution in cylinder and intake-port can be expected. Another conventional method is to set a uniform initial condition for A/F distribution in intake-port. And the first scheme takes too much time, while the second one no so accurate. In this paper, we developed a methodology to consider realistic physical phenomena in intake-port with low computational requirement. At first, the physical phenomena, including fuel injection, adhesion, and evaporation, should be simulated in the intake-port alone. And in the following step, the detailed distribution of remaining fuel would be used as an initial condition, and vaporization process in intake-port would be coupled to in-cylinder simulation transiently. Finally we can predict the mixture distribution in the whole cylinder. And we compared simulation results from conventional uniform-initial-condition scheme and the new scheme. And we found that the conventional scheme couldn’t take the vaporization from intake-port wall into consideration, and it result in a fresh air in-flow in late intake stroke. And our new scheme can predict this vaporization, and the result shows the in-flow in intake-stroke and mixture distribution in cylinder are different from the former scheme. Finally we concluded that the new scheme considering intake-port phenomena is an effective method to simulate mixture distribution in PFI engine, and it gives us a more realistic result. And with this methodology, we can analyses the disadvantage and corresponding root cause of a specific PFI engine in a limited time.