Diesel particulate filter has been adopted in new vehicle with diesel engine. Since the flow of exhaust gas was clogged as particulate matters were deposited in the filter, it have bad effects on a fuel consumption and power. It was investigated that a particulate filtering system with vacuum pump in the exhaust gas line could be free from clogging in previous research. In this study, the effects of water injection and position of inlet port in filtering system on reducing in particulate matter were investigated. It was noticed that particulate matter were decreased remarkable by water injection and moving the position of inlet port.