Procrastination is one of the most common behavior problems of human beings, which not only affects the efficiency of work and study, but also causes harm to physical and mental health. Therefore, indepth research on the causes and formation mechanisms of procrastination behavior has important scientific value, and also has important practical significance for intervention and prevention of procrastination. Based on the knowledge of theoretical mechanics, this study introduces the concepts of procrastination-force, and then gives the three main factors of procrastination in mechanics, including pressure, difficulty coefficient and heart-force, and constructs a mechanical model of doing things. According to this model, it can be seen that there is a critical state of procrastination, and the problem of procrastination can be solved when the values of pressure, difficulty coefficient and heart-force are properly changed. The experimental results show that the model can transform the solution of procrastination into a simple mechanical problem, not only enrich the understanding of procrastination behavior, but also provide an effective way to avoid the phenomenon of procrastination.