The probability analysis was used in this paper. Natural frequency and of Excitation force fre- quency of every component in shafting system were considered to be the random variable. The distillation functions of natural frequency and of excitation force frequency were analyzed on the basis of special struc- ture and stress conditions. The dynamic reliability model of the axis was set up and dynamic reliability of the designed axis was worked out to provide the reference for structure designing; of axis.