In this paper, a kind of on-board liquid hydrogen (LH2) cold energy utilization system for a heavy-duty fuel cell hybrid truck is proposed. Through this system, the cold energy of LH2 is used for cooling the inlet air of a compressor and the coolant of the accessories cooling system, sequentially, to reduce the parasitic power, including the air compressor, water pump, and radiator fan power. To estimate the cold energy utilization ratio and parasitic power saving capabilities of this system, a model based on AMESim software was established and simulated under different ambient temperatures and fuel cell stack loads. The simulation results show that cold energy utilization ratio can keep at a high level except under extremely low ambient temperature and light load. Compared to the original LH2 system without cold energy utilization, the total parasitic power consumption can be saved by up to 15% (namely 1.8 kW).