Presented in this paper is the energy flow distribution of a diesel engine turbocharged system, on the basis of a combined method of one-dimensional gas dynamics simulation and dyno tests. By analyzing the flow path of exhaust gas energy flow from turbine to compressor and then intercooler, the exhaust gas energy recovery potential by turbocharging was obtained, and the energy flow characteristics in the diesel engine turbocharged system was analyzed. The results have shown that the energy recovery potential is strongly dependent on the engine's and the turbo's operational conditions. About 13% of engine exhaust gas energy could be recovered by the turbocharger when the latter works in the high efficiency domain, while only about 6% could be recovered in the low efficiency domain. Under all operational conditions, around 2% of the recovered exhaust gas energy is used to boost the intake gas pressure, and the rest is taken away by the intercooler. The results have provided theoretical basis and fundamental data for engine fuel saving through exhaust gas energy recovery by turbocharging or turbo-compounding.