Predicitions of swirl velocity in an engine using the simplified simulation model were compared with the experimental data. The flow velocity was measured in a test engine by the laser doppler velocimeter under the motored condition. The predicted results of spatial distribution of the tangential flow velocity on a cylinder diameter and time history of the averaged angular velocity were compared with the experimental data. The flow patterns in the cylinder and the trends of angular velocity at the compression and expansion stroke are in good agreement with each other. It is confirmed that this simulation model is valid to predict the mean flow velocity in an engine. But this cannot predict the flow pattern at the intake or exhaust process at which the un-uniformity of flow exists.