The effect of random initial geometric imperfections on the vibration behavior of rectangular plates is investigated in thii paper using a statistical method. The random initial geometric imperfections of plates are described by Gaussiun random fields and simulated numerically using EWwko~s method. Lindstedt-Poincark’sp erturbation technique is employed to solve Du@tg’s Equation with an additional quadratic spring term derived in the vibration analysis of imperfect rectangular plates. A Nonre Carlo analysis for simply supported plates is carried out in detail to illustrate the proposed approach. It is shown that the effect of random geometric imperfections on the vibration behavior of the plates can be described quantitatively in terms of the frequency reliability function and the hardening type probability.