Abstract: The evaluation and classification of signal quality play an important role in extracting fine features of signals and identifying radiation source targets. This article focuses on the research of S-mode response signals of IFF radiation source targets and proposes a two-level quality assessment and classification method. The evaluation and classification process is detailed from two levels: initial signal quality assessment and precise signal quality assessment, achieving accurate evaluation and classification of the S-mode response signal quality of IFF radiation source targets. This provides basic support for the subsequent extraction of fine features of IFF signals and the recognition of radiation source targets. This article conducts experimental verification using target data from multiple civil aviation radiation sources of different quality types. The experimental verification results show that the quality assessment classification accuracy of the proposed method in this paper reaches 95.3%. By selecting the corresponding quality type signals, the effectiveness of feature extraction can be significantly improved. Furthermore, the accuracy of IFF radiation source target classification and recognition has been improved by 17.2%.