The chemical components of the toxic and effective parts of the Mongolian medicine Euphorbiae Fischerianae Radix were analyzed using ultra performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-Q-TOF-MS/MS).The differences in the compounds contained in the petroleum ether,dichloromethane,ethyl acetate,and n-butanol fractions of Euphorbiae Fischerianae Radix were compared.The results showed that,through comparison with the literature and the database established in the laboratory,68 compounds were identified.Among them,there were 43 diterpenoids,five triterpenoids,eight coumarins,two phenolic acids,two tannins,three acetophenones,one sterol,one alkaloid,one fatty acid,one phloroglucinol,and one other type of compound.The UPLC-Q-TOF-MS/MS technique used in this study provides a rapid and efficient qualitative analysis method for identifying the chemical components of the toxic and effective parts of Euphorbiae Fischerianae Radix.This study not only offers a scientific basis for the research on the chemical components of the toxic and effective parts of Euphorbiae Fischerianae Radix and the toxicity assessment of this herb,but also provides experimental data for the further development of the medicinal value of Euphorbiae Fischerianae Radix.