After in-depth study of OSEK/VDX operating system specification, a method of conformance test for OSEK/VDX operating system based on classification tree is proposed. This method works as follows: first, test purposes are extracted from the OSEK specification; next, according to the specification and test purposes, classification tree is constructed and the input domain of the classification tree is divided; then generation and constraint rules are added to the tree; finally, conformance test cases are automatically generated with the help of CTE XL tool. The effectiveness and correctness of OSEK/VDX operating system conformance test using classification tree method are proved through the conformance test of MiniOSEK.