Abstract: Based on a randomness of variable load on underwater crossing pipeline, using stable binomial random process as a probability model of variable load and by means of a basic characteristic of the model, obtains an applicable relational expression between probability distribution function F_M(x) of maximum variable load value within design base period and probability distribution function F(x) of random point. As for the dynamic water load on underwater crossing pipeline naked and suspended, relative model theory is used to calculate pipeline's dynamic response extent value, thus obtains the dynamic stress on pipeline, and finally divides the pipeline into such three service stages as empty pipeline statue, normal operation statue and naked and suspended statue according to load statue in pipeline's service span, and makes a load effective combination of pipelines with the three statues. This statistic analysis method for variable load conforms to real situation of variable load on service underwater crossing pipeline and its result offers an reference to underwater crossing pipeline's reliability analysis and design.