Design reliability of the railway wagon axle with 30 ton axle weigh is assessed on a basis of the code EN 13103 loads set. Constraint effects of the interference fits between wheels – axle and bearings – axle are taken into account. Integrated wheelset model of finite element method is applied to calculate the axle stresses, in which the rail pieces, wheels, axle, bearings, and adapters are fitted and analyzed together. Results reveal that the maximum stress section is at outer side close to wheel seat, different from the prediction of inner side close to wheel seat by the code analytic method. Under requirement of 3, 000, 000 km and 99 percentage of confidence, the evaluated axle design reliability is 0.9987 if manufacturing by the existent LZ50 axle steel. And if by the material EA1N or EA4T of the code EN 13103, the present design meets also the requirement of the code EN 13103.