Based on the Stirling heat engine model, a new method for measuring the system moment of inertia is proposed. This method eliminates the need to disassemble experimental setups. By simply connecting a load generator to the running Stirling heat engine system, the moment of inertia can be indirectly determined through measurements of the load generators output power, along with angular acceleration and angular velocity during the deceleration phase after loading. Comparative experiments with the traditional moment of inertia measurement methods demonstrate that this approach exhibits high validity and accuracy. The proposed method provides new perspectives and research pathways for measuring the moment of inertia in structurally complex experimental systems or those difficult to disassemble. It provides new ideas and application value for measuring the moment of inertia of flywheel systems driven by different types of driving forces.