The safety coefficient given in the design codes of railway vehicle structure has certain experience. In this paper, based on the reliability theory, the method of reliability safety coefficient evaluation is adopted, which makes the selection of safety coefficient more reasonable. A certain type of high speed train carbody was taken as research object, the finite element model was established. Based on the code EN 12663-1, the static and fatigue loads were determined, which is considered the aerodynamic load in condition of high speed passing. After the static strength analysis of carbody, the fatigue strength was analyzed using the reliability Goodman curve of carbody material. Finally, established the relationship of reliability and safety coefficient, the safety coefficient of static strength and fatigue strength of the car body with different reliability were obtained. The results show that the static strength and fatigue strength of carbody meet to the requirement under the different reliability. With the increase of the reliability, the safety coefficient is reduced. The minimum safety coefficient of static strength under reliability of 99.90% is 1.3, and the corresponding load condition is the preparation condition combined with 1 500 kN longitudinal compression load. In aspect of fatigue strength, the locations with small safety coefficient mostly appear in the door’s corner and the window’s corner of the carbody sidewall. The minimum safety coefficient of fatigue strength 1.53, which has a certain safety margin. The dispersion of carbody stress and material strength have influence on the safety coefficient. In order to ensure the high reliability of the high speed train body, it can take measures to control the strength properties dispersion degree of aluminum alloy materials, reduce the stress concentration of the geometrical structure and reduce the working stress and so on.