OBJECTIVE To compare the chemical components contained in Artemisiae Scopariae Herba （ASH） standard decoction and its decoction pieces， and provide foundation of their pharmacological substances. METHODS ASH standard decoction and its decoction pieces were prepared； UFLC-Q-TOF-MS/MS method was used for the detection in the negative ion mode， and the total ion chromatogram was extracted by the PeakView 1.6 software. By comparing with reference substances， literature data， and online search of compound database such as PubChem， the chemical components contained in ASH standard decoction and its decoction pieces were identified and analyzed for the differences. RESULTS A total of 125 chemical components were identified in ASH standard decoction and its decoction pieces， including 50 organic acids， 39 flavonoids， 3 coumarins， 2 amino acids， 5 lignans， and 26 others. 3-methoxy-caffeic acid-4-O- β -D-glucoside， p-hydroxybenzoic acid， caffeic acid 4-O- glucoside， spiraeoside， and phenyl β-D-glucoside in ASH standard decoction were not detected in its decoction pieces， while 6′-6′ chlorogenic acid dimer， quercetin-5-glucoside， apigenin 7-methyl ether 5-（6″-malonylglucoside）， quercetin-3-O-arabinoside， 6″-caffeoylhyperin and 6-O-caffeoyl-D-glucoside in decoction pieces were not detected in the standard decoction. CONCLUSIONS Most components in ASH decoction pieces are transferred to its standard decoction， but a few components undergo chemical reactions in whole or in part during the boiling process， transforming into other or new components in the standard decoction.