In order to meet the requirement of DPF active regeneration temperature, the effect of intake throttling on performance of diesel engine was studied. In a highpressure common rail diesel engine with inlet pipe equipped with electronic throttle, the effects of intake flow on excess air coefficient, specific fuel consumption, exhaust temperature and emission characteristics were studied under low, medium and high loads at 1 600 r/min and 2 000 r/min based on different throttle close degrees. The test results show that the excess air coefficient decreases gradually with the closing of throttle and drops by 14% at most under the condition of low speed and medium load. The specific fuel consumption first decreases and then increases with the increase of throttle close degree. The intake throttling can significantly increase the exhaust temperature. In addition, the increase of intake throttling will lead to the deterioration of CO and soot emissions, and THC and NO_x emissions will improve at a small close of throttling.