In order to have a further research on pneumatic regenerative braking system, a simulation model was established and validated based on the experimental test bed. Then, the effects of air compressor displacement and accumulator volume on the regenerative braking process were analyzed. The analysis results showed that the vehicle cannot be stopped within 100 s at the initial speed of 120 km/h by using the energy recovery system alone when the accumulator volume is 12 L, the accumulator maximum pressure is 3 MPa, the air compressor displacement is 560 cc/r, and the vehicle mass is 1699 kg. And the regeneration efficiency is 5.7% at the same condition. Further analysis showed that the energy recovery system is greatly affected by the accumulator volume and the air compressor displacement. Both of these factors increase the braking distance of the vehicle. However, the energy regeneration efficiency improves with an increase in the accumulator volume, while it is less affected by variations in the air compressor displacement.