A new model, a model of random nonprobabilistic reliability, to evaluate the structure reliability was established based on the theory of random probability and interval non-probabilistic reliability for the randomness of material properties and loads of vessels in-service, and for region character of hull resistance testing result under the inspection of corrosion damage. Furthermore, the method to calculate the reliability index of the new model was investigated in the view of random variables and interval variables mutual transformation. Based on this new model, the reliability of vessel hull structure yield strength was analyzed. The result shows that the model can well reflect the objective uncertainty of structure variables as well as abate the conservatism of evaluation results, and has a strong applicability in reliability evaluation of ships in-service which contain the random variables and the interval variables simultaneously.