Abstract: To address the difficulty of installing specialized measurement equipment and the deterioration of measurement accuracy caused by vibration during practical diesel engine operation, an indirect testing method combining parameter measurements and numerical simulation was proposed. Based on steady-state and dynamic loading test data obtained from an engine test bench and analytical relationships between engine performance and key control parameters, combustion characteristics, brake specific fuel consumption and effective torque under dynamic conditions were expressed as functions of known electronic control unit parameters or easily measurable parameters, including engine speed, injected fuel quantity per cycle, injection pressure, and main injection timing. A simplified model was then employed to indirectly calculate engine performance. Comparison of simulation results with experimental data under steady-state and dynamic conditions demonstrates the effectiveness and prediction accuracy of the proposed method.