For the vehicles with frequent stop-start operations, fuel consumption can be reduced significantly by implementing stop-start operation. As one way to realize this goal, the pneumatic hybrid technology converts kinetic energy to pneumatic energy by compressing air into air tanks installed on the vehicle. The compressed air can then be reused to drive an air starter to realize a regenerative stop-start function. Furthermore, the pneumatic hybrid can eliminate turbo-lag by injecting compressed air into manifold and a correspondingly larger amount of fuel into the cylinder to build-up full-load torque almost immediately.This paper takes the pneumatic hybrid engine as the research object, focusing on evaluating the improvement of fuel economy of multiple air tanks in different test cycles. Also theoretical analysis the benefits of extra boost on reducing turbo-lag to achieve better performance.A six-cylinder pneumatic hybrid diesel engine model is built in the MATLAB/Simulink environment with Stateflow®. Based on this model, a pneumatic hybrid vehicle driving cycle simulation program has been applied to analyze the charging and discharging processes during various bus duty cycles. The analysis shows that the pneumatic hybrid engine can reduce fuel consumption by at least 5% by realizing stop-start operation, and eliminate 90% of the idling time. A new engine concept and structure which can realize the boost engine function has been proposed. The theoretical analysis of this engine is also given out.