Abstract: The analytical method for identification of the toxicosis in blood was established by gas chromatography mass spectrometry(GC/MS) based on the practical clinical case. 5 mL blood sample of the patient was adjusted to pH4—5 with 10% H 3PO 4, then diluted by 15 mL methanol/acetone (1∶1, v/v ). After supersonic vibration, dehydration with Na 2SO 4, and filtered mixture was concentrated to 1 mL. The extracted sample was comprehensive analyzed and ten toxic components were identified by GC/MS. The main toxic components were furfural, 5 methyl furfural, 5 hydroxymethyl furfural, and 2,3 dihydro 3,5 dihydroxy 6 methyl 4H pyran 4 one, etc. The analytical results provided scientific evidences for salving this kind of patients.