Objective To study the injury risk and fatigue status of firefighters with different training postures under load-bearing conditions to reduce the occurrence of physical injuries and occupational diseases. Methods First, a questionnaire was administered to investigate the training injury conditions of firefighters in a fire-rescue brigade. Considering the exercise fatigue factor, which accounts for the highest proportion of injury causes, lower back analysis, static strength analysis, fatigue analysis, comfort analysis, and other human factor analysis tools in Jack software were used to analyze four common firefighter water-shooting training postures. Training postures while climbing a five-storey building with loads and a hooked ladder were also simulated. Results Injury caused by exercise fatigue accounted for 69.8% of injuries and was the most important injury-causing factor. The risk of knee and ankle joint injuries increased in all four water-shooting postures. The comfort levels of the four water-shooting postures from high to low were shoulder, standing, kneeling, and lying postures. For the entire dynamic training process, while climbing the five-storey building with loads and climbing the hooked ladder, firefighters did not have an increased risk of lower back injury but had an increased risk of ankle and knee joint injuries. Conclusions Some training postures are uncomfortable for firefighters, and they experience body discomfort during firefighting training with loads, thereby increasing injury risk. These results provide scientific references for the prevention and reduction of firefighter training injuries, reasonable training plans, and targeted protective measures.