Therrnal cracking within mass-concrete structures is one of themes of today's concrete technology. How to evaluate thermal stress that causes thermal cracking exactly is the most basic subject in it. Up to now, State theory method and Rate of flow method are proposed to apply F. E. M. thermal stress analysis. This paper describes precision and utility of these two methods. As a result, State theory method has question about creep Poisson's ratio of 0.5 and Rate of flow method generates slightly greater thermal stress.