Objective To use metabonomics method to study the potential syndromes markers about lung and defensive Qi deficiency syndrome of repeated upper respiratory infection（ URI） and observe clinical effects and possible mechanism of action of Yupingfeng Particles. Methods Fifteen patients with lung and defensive Qi deficiency syndrome of repeated URI（ disease group） were given Yupingfeng Particles

5 g each time

three times a day for a total of 60 days. Eighteen healthy subjects were collected as health group at the same time. Blood samples from the healthy and the disease group were collected before and after treatment. High performance liquid chromatography mass spectrometry instrument（ HPLC-MS） was used to detect plasma metabolites

and principal component analysis（ PCA） and partial least squares（ PLS） was used to make statistical analysis to the data for comparing plasma metabonomics original spectra and data of the healthy group and the disease group before and after treatment. Results After treatment

clinical symptoms such as susceptibility

chills

spontaneous perspiration of patients in the disease group improved significantly（ P < 0. 01）. Curative effect of traditional Chinese medicine syndrome in the disease group showed that clinical recovery were 4 cases

7 cases were markedly effective

3 cases were effective and the total effective rate was 93. 34%. Metabolic spectrum of the disease group was significantly different from the health groups before the treatment. The disease group’s metabolic spectrum has significant changes after Yupingfeng Particles intervention

regressed to the health group. Four kinds of material including Cysteine

L-methionine

threonine

pyroglutamic acid were potential syndrome markers of lung and defensive Qi deficiency syndrome of repeated URI. Conclusion Patients with lung and defensive Qi deficiency syndrome of repeated URI had disorder of amino acid metabolism. Correcting disorder of amino acid metabolism may be one of the mechanisms of action that Yupingfeng Particles in treatment of lung and defensive Qi deficiency syndrome.