The traditional research of turbocharger and gasoline engine numerical matching focuses on full load condition, but the reasonable matching for single working condition of full load cannot guarantee reasonable matching of turbocharger and gasoline engine throughout the scope of work. For the limitation of turbocharger and gasoline engine numerical matching on single full load condition, the basic principle of the three-line condition method was introduced. The full load thermodynamic model of direct injection turbocharged gasoline engine was built by using GT-Power software, and the model was extended to part load condition to be applied to the thermodynamic model of the three-line condition method. The thermodynamic model was applied to the matching research of three turbochargers. The results indicate that the three-line condition method can directly reflect the problem of the original turbocharger and engine matching throughout the scope of work, and the matching performance can be improved by using this evaluation method to rematch turbochargers.The method of three-line condition overcomes the limitation of studying only on single full load condition, and provides a numerical evaluation method for the preselection and optimization of turbochargers.