To solve the issues of low thermal efficiency and high emissions caused by long injection duration and poor atomization quality of single injector mode under high-load condition of diesel engine, the diesel dual direct injection strategy was proposed. The combustion and emission characteristics of single and double injector modes under high-load conditions were studied by experiments, and further analyzed in detail by computation fluid dynamics（CFD）simulation method. The results show that the dual direct injector mode presents three stages of heat release. The first stage is the low temperature heat release of the auxiliary injector, the second stage starts from the high temperature heat release of the auxiliary injector, and the third stage is the high temperature heat release caused by the main injector. In addition, the ignition timing under the dual direct injection strategy is advanced, and the center of combustion is closer to the top dead center, thereby leading to the higher thermal efficiency.