Abstract: This Paper analyzes the mechanical characteristics of a rotating disk when its geometric shape is a random quantity，and derives the computational expression of the random stress field and reliability of the disk by second一order perturbation method. Simple conputational examples are used to analyze the law that the geometry of the disk affects its reliability, and
the results of the examples，compared with Monte Carlo simulation results，show that the method in this paper is effective and the theory is right.

Key words: Rotating disk, Reliability, Probability