Stochastic loads are classified three types: dynamic load accumulation, amplitude and obey the Poisson distribution whose parameter is , loads changing with time and not obey any distribution. As these conditions, their dynamic reliability computing formulas are established under structural strength without degeneration and structural strength with degeneration by using stress-strength interference theory and stochastic process theory; it shows that the reliability of the structure is gradually reduced with time, but not unchanged. Finally, three numerical examples to illustrate the models are correct, feasible and practicable.