Abstract: The reliability of ceramic package devices have always been the attractive topic of electronic package. Many previous researches used a uniform temperature assumption to study the fatigue life of solder joint under thermal cycle through the finite element analysis method. But the internal temperature field of ceramic packing is not uniform in fact, because of its special nature of the material. In this paper, by using the ANSYS finite element software, the reliability of the 16×16 ceramic ball grid array (ceramic ball grid array, CBGA) package model under thermal cycle load was carried out based on the classical theory using hexahedral grid. Considering the internal temperature field distribution of the CBGA components under thermal cycle load, the rationality of the uniform temperature assumption under different conditions are discussed. And the simulation results show that the predict fatigue life under the condition of non-uniform temperature distribution is lower than the one with uniform temperature assumption conditions. Through the above discussion, the judgment can be provided for the usage of uniform temperature hypothesis.