Crystallizer is a key equipment of the 1.2 million tons production line. It is a complicated shell structure and a large but thin machine. The power mixing process is a typical property of the crystallizer. So the structure reliability and the modal of crystallizer should be analyzed. The structure strength, safety coefficient and multi modal are analyzed by COSMOS which is large scale finite element software. The results show that the static strength of the support part meets the requirement, the weakest part of the crystallizer is the weld point, the steel beam with the equivalent stress is 260 MPa, safety coefficient is 1.243 and the stability of crystallizer main structure under dynamic disturbance meets the requirements, thus resonance doesn’t occur.