Many countries of the world has been devoting a lot of effort to reduce carbon emission. In order to reduce carbon emission, the high efficiency engine has been studied in the automotive industry. Of these, the spread and research of the diesel engine in Europe center are active. However the combustion characteristic of diesel engines have disadvantages of much NOx and soot emissions. In this study, the optimum regeneration point of the forced regeneration type DPF(Diesel Particulate Filter) that was equipped in medium-duty diesel vehicles using a mechanical fuel injection system have studied. DPF that is applied to the medium-duty diesel vehicle has a bent inlet pipe. The flow distribution characteristics of DPF according to the influence of the bent pipe have investigated. The flow distribution characteristics of DPF according to variation of the engine operating condition is considered to be useful data In order to decide the optimum regeneration point.