AOP gains increasing focus in Programming Technology. Its ability of handling crosscutting concern supplements all programming methodology to deal with the concerns that cannot be further refactored out, which results in tangled code scattered throughout all modules, The implementation of AOP makes it likely to have ability modifying source code in a distinctive way. That is, without changing any source code, modification is merged at compile time or runtime dynamically, so that it can change execution process accordingly. However, AOP has its restrictions; one example is that it is difficult to alter code context inside a function. Thus, a case study will be applied in this project for the purpose of investigating AOP modifiability, which aims to find out all related issues and significance of AOP system modification.