The dynamics model and model-based controller (LQG servo controller) have been constructed to improve performance of diesel engine at transient condition. The input parameters of the dynamics model are injected fuel quantity, injection timing, external EGR ratio and boost pressure. In the model, one cycle is discretized into 7 representative points such as EVC, IVC, fuel injection, ignition, maximum pressure, EVO and IVO. The precision of the prediction of the model and the responsiveness of the controller were checked.