An oracle is a mechanism commonly used for determining whether a system has passed or failed a test, which is very important for software testing. A log file, used to record the history of software’s behavior, provides a means for debugging and testing. Log file analysis (LFA) is a lately applied approach for test oracle, having shown its applicable prospect in software testing. To achieve the better feature of general purpose, we propose a practical test oracle framework based on log file analysis, presents a 7-tuple state machine model for the analyzer and designs a description language to describe the state machine. The data structures and the algorithm for the implementation of this method are also given. Experimental results show this method can be easily used to test software whether on system-testing level or unit-testing level, suitable for various software testing.