By comparing the characteristics of various turbocharging system, then hybird turbocharging system is proposed. In principle the technical approach of hybrid turbocharging system is analyzed to solve the steady and transient condition problem about vehicle diesel engine. Then several modes of energy flow about hybrid turbocharging system are analyzed, and calculation processes about each share of the energy flow are given. According to the characteristic of turbocharged diesel engine, the energy flow distribution of the two typical engine conditons is calculated. Analysis of energy flow is of great significance to properly distribute the energy share and improve the performance of the turbocharging system.