Software component adaptation is widely recognized to be a crucial problem in componentbased software engineering. In this paper, we focus on the signature level component adaptation such as names, parameters and propose a checking mechanism to find the signature level mismatch. A component model is designed firstly in mathematical specification which can give more details to find and adapt the signatures that have a mismatch with the user need. Some notations and definitions are given to help the checking of signature level mismatch and then a checking mechanism of signature level mismatch with the use of context-free expressions is proposed. Our proposal is based on the more details provided by the user, and is supported by dedicated algorithms. At last future work and limitation of the checking mechanism are discussed.