Fuzz testing is a software testing technique,which provides invalid, unexpected, or random data to the inputs of a computer program to test the robustness and security of procedures[1]. For structured data like logging, the variant fuzz testing framework adopts a configuration file, apply traverse and stream processing to complete the structured fuzzing. This article starts with the features of the structured data, then introduces the design and implementation of the variant fuzz testing framework, including function modules, class structure, and logic processing. As a conclusion, this framework is compared with zzuf tool, and the advanced nature of this framework is elaborated.