To reveal the soldier’s Acute Stress Reaction Characteristics when implementing major military tasks, we used the "acute stress reaction scale " to test them and then compared each task. We got the results subsequently that the soldier’s acute stress response in each dimension and total response index had a significant difference under the five major military tasks. Besides, the significant differences were mainly in cognitive change and emotional change. The extent of acute stress reaction was influenced by the exposure factor. The symptoms of soldiers’ acute stress reaction had a significant positive correlation with work efficiency which was influenced mainly by physiological responses, anxiety, and attention deficit and self-blame. So we got the conclusion that with the different nature of the major tasks and exposure factors, the soldier’s acute stress reaction was significantly different, and had significant impact on the effectiveness when carrying out military task.