The invention discloses a partial flow equivalently-dynamic diluting and sampling system for diesel engine exhaust particles and a control method, belonging to the technical field of engine emission tests. The partial flow equivalently-dynamic diluting and sampling system is used for splitting the flow of engine exhaust with a constant ratio and introducing the engine exhaust in a diluting air duct by virtue of a flow-splitting and diluting pipeline with closed-loop feedback control, mixing the engine exhaust with clean air to form uniform diluted exhaust gas, introducing the diluted exhaust gas with a constant ratio in a sampling channel filter paper retainer by virtue of a particle sampling pipeline with closed-loop feedback control, collecting the exhaust particles by sampling filter paper placed in the retainer, and then detecting the emission level and the constituents of the diesel engine particles; the partial flow equivalently-dynamic diluting and sampling system can realize two-way transmission for data by an upper computer and a lower computer via an RS232 serial port communication protocol and a customized data format; and compared with the existing test system for diesel engine exhaust particles, the system has no need of a mass flow meter and an exhaust concentration analyser, and has the advantages of being high in control accuracy and low in test and maintenance costs.