Abstract: Class is the basic unit to object-oriented program testing. On the basis of data-flow testing, an expended class control flow graph(ECCFG) was introduced in this paper, it improved class control flow graph algorithm to analysis the def-use pairs in intra-method, inter-method, intra-class and inter-class, which effectively solved the problem of inadequate coverage caused by focusing on single class testing and ignoring the inheritance of object-oriented program.