CONCLUSIONS AND FURTHER WORKSFrom the perspective of meeting the requirements of applications interoperation, this paper proposes that the nature of interoperability testing between operating systems is API testing related to interpretation functions. To illustrate this point, this paper first introduces the theory of protocol testing into interoperability testing between operating systems, which provides theoretical basis for test method. Then test strategy and test model based on TTCN-3 according to the feature of interoperability testing between operating systems is presented, and the key point in test case design and running environment is given. Lastly this paper makes the evaluation classification for interoperability between operating systems.