Equipping diesel engine with intake throttle valve is one of the ways to raise exhaust temperature of low load conditions and improve emission, but it will affect other performances of diesel engine. In the following, the effects of intake throttling on low load performance of diesel engine were discussed. The experimental results showed that intake throttling would result in the increase of exhaust temperature and NOx emission. In addition, the incylinder pressure decreased, the average combustion temperature and mechanical efficiency increased, the ignition delay period extended and the combustion starting point retarded. The brake specific fuel consumption and smoke increased with the increase of throttling degree under the conditions of low load at medium and low speed, but would decrease though hrottling under the conditions of low load at high speed. At speed of 2 500 r/min and torque of 29 N·m, the NOx and smoke emission of diesel engine with fully open EGR ecreased with the increase of throttling. The brake specific consumption, NOx and smoke emission decreased by 7.9%, 58.1% and 27.3%  respectively and the exhaust temperature increased by 42.5% when the intake mass flow decreased from 191.4 kg/h to 140.6 kg/h.