As the hub of power transmission for special vehicles, the multi-source integrated power system plays a critical role in vehicle performance through its safe, stable, and reliable operation. In response to the safety risk assessment requirements for integrated power systems in special vehicles, a short-term online safety risk assessment method was proposed based on equipment participation degree. First, a comparative analysis was conducted in terms of circuit configurations of direct-connection and controllable integrated power systems, and a four-level safety risk indicator system was established for multi-source integrated power systems in special vehicles. Second, a quantitative safety risk assessment model was developed comprising four units (power supply, distribution, load, and system), with quantitative calculation expressions determined for the safety risk assessment model of each unit. A comprehensive weight calculation method was designed to conduct overall system safety risk assessment based on equipment participation degree, and to determine corresponding safety levels. Finally, using a case study model of a multi-source integrated power system for special vehicles, different operating conditions were simulated to verify the effectiveness of the constructed safety risk indicator system and assessment method. The results show that the established safety risk indicator system can quantify the system risk level and classify safety grades, and is applicable to on-line risk assessment under various operating conditions.