According to the application of VNT-EGR technology on China VI diesel engine, the influencing laws of VNT and EGR coupling on the economy and emission characteristics of diesel engine were studied. Then the optimization of diesel engine matching was conducted through the orthogonal experiment of VNT and EGR valve opening combined with the injection parameters. The results show that the efficiency of turbocharger shifts to the lower area due to the decrease of available exhaust energy caused by increasing EGR valve opening when VNT and EGR run at the same time, which can be improved by decreasing the VNT opening. Under the same EGR valve opening, reducing the VNT opening can improve the airfuel ratio of diesel engine. As for the same smoke emission level, a larger EGR rate can be achieved and the NOx emission can be further reduced. Therefore, the overall emission level of soot and NOx decreases. With the decrease of VNT opening, the brake specific fuel consumption reduces first and then increases due to the pumping loss and in-cylinder combustion. The NOx emission reduces greatly, soot and fuel consumption increase, and the economy improves at low speed and high load because of the orthogonal optimization of VNT and EGR valve opening. With the optimization of injection parameters, the economy can be optimal under the condition of meeting NOx emission target.