The study aims to investigate the chemical composition transformation patterns of differently processed Cassiae Semen decoction pieces and to establish a scientific evaluation standard for this Lingnan-region herbal medicine. Based on UPLC-Q-TOF-MS² combined with Feature-Based Molecular Networking （FBMN）， the composition differences of raw Cassiae Semen， stir-fried Cassiae Semen and carbonized Cassiae Semen were analyzed， and the HPLC fingerprints of different processing specifications of decoction pi

eces were constructed. FBMN identified 90 compounds， with 40， 42 and 36 compounds （35 shared compounds） were detected in the three types of decoction pieces respectively. The deepening of processing resulted in the breakage of glycosidic bonds of glycosides （e.g. cassiaside B₂， rubrofusarin gentiobioside，etc.） and the increase of aglycone content and partial degradation. The discrimination standard was established by the ratio of peak area （RPA） of six transformation-related characteristic peaks： RPA≤0.100 for raw Cassiae Semen；0.200≤RPA≤0.500 for stir-fried Cassiae Semen；RPA

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0.500 for carbonized Cassiae Semen. UPLC-Q-TOF-MS

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/FBMN could be used to elucidatedynamic transformations patterns of processing， and the RPA index of HPLC fingerprint could provide a scientific basis for objective differentiation of processing specifications and determination of endpoint.