Abstract: Time-variant reliability problems appear in the engineering practice when loads stochastically change or the material properties of the structure deteriorate in time. In this paper, a time-variant structural reliability analysis method for non-linear limit-state function is presented. In this method, the stochastic process in the limit-state function is first discretized. Each discretized limit-state function is linearized at the most probable point (MPP), and it is further simplified into a time-invariant reliability analysis problem which is then solved by using the traditional first order reliability method (FORM). Three numerical examples are analyzed to demonstrate the effectiveness of the present method.