Some equipment of special types can be stored for a very long time. During storage, the equipment can be affected by temperature, humidity, mechanical stress, and so on, and the study on their storage reliability is very significant. Many theories and methods are proposed for storage reliability assessment in the literature, but few are applied into practice or verified by the actual conditions of the engineering project. Besides, the performance degradation of the equipment with a long storage time is not evident, the performance degradation model is hard to build. Thus, in this article, a storage reliability assessment method under periodical inspection for the equipment with a long storage time is studied. In the method, the storage reliability curves of ''repaired as good as new'' and ''degenerated after repaired'' are constructed to describe the different states of the stored equipment after periodical inspection, the environmental factor is used to deal with the data coming from accelerated life tests, and the study is based on an engineering project, thus the effectiveness can be verified.