Abstract: Aimed at reduction of smoke emission, the influence of fuel injection strategies on combustion and soot emission was conducted in two-stage turbocharged diesel engine with a by-pass valve under typical 5s transient process of constant speed and increase toque. The test results show that: two-stage turbocharger can be allowed to improve intake air supply, and provide significant soot reduction as the valve was closed under full-stage rail pressure augment strategy, but soot deterioration happened once valve opening got larger; with small valve opening, sectional-stage fuel injection augment strategy can be provided to improve in-cylinder thermodynamics conditions during early transient process, and then enhance air-fuel mixture much more better at larger load rate, and maximum soot decline reached up to 51.5%, which happened with valve opening by 10%; fuel consumption could be getting worse as well when valve opening became larger, but this deterioration situation can effectively be restrained by utilization of sectional-stage fuel injection augment strategy.