In order to improve the emission performance of sequential turbocharging diesel engine during the process of acceleration and loading, the modification of air injection system for the intake manifold was conducted, the control and measurement system of transient process was established, and the air injection experiment was carried out in the process of acceleration and loading. By studying the influencing laws of injection pressure and orifice diameter on intake pressure, maximum combustion pressure, mean effective pressure and emission performance, the air injection strategy was achieved and the transient performance of sequential turbocharging diesel engine during the process of acceleration and loading improved effectively.