Migrant workers and their employers to sign the usually short-term or no fixed term labor contract, some construction units and even temporary employment personnel every day, maybe even employees do not understand the basic situation once an accident occurs, especially for certain chronic occupational disease, because it is difficult to determine the time, place, difficult to gather sufficient evidence and related diagnostic proof vest because of unknown things, the responsibility is difficult to identify, the enterprise is often shirking of responsibilities, leading victims rights of migrant workers in the road around the wall, interests can not be guaranteed.