Objective To explore the potential metabolic biomarkers of Wei Qi monthly physiological changes.Methods The beginning of the month（ 1st Aug. of the lunar calendar）

the middle of the month（ 15 th Aug.） and the end of the month（ 30 th Aug.） were set by the lunar calendar month with autumnal equinox. Ten SD rats were sampled from posterior orbital venous plexus at midday 12: 00 on corresponding days. Plasma metabolites were detected by high performance liquid chromatography / mass spectrometry instrument. Data was analyzed by principal component analysis and partial least square method. Plasma metabonomics data in each group were compared. Differential metabolic markers in each group were explored. The potential metabolic biomarkers of Wei Qi monthly physiological changes were inferred. Results Compared with the middle of the month

7 differential metabolites on the beginning of the month might be possible markers to distinguish between the two groups

while 8 differential metabolites on the end of the month might be possible markers to distinguish between the two groups. Compared with the end of the month

9 differential metabolites on the beginning of the month might be possible markers to distinguish between the two groups. Four differential metabolites（ including eicosapentaenoic acid

cortisol

proline and dimethyl fumarate）were inferred as the potential metabolic biomarkers of Wei Qi monthly physiological change. Conclusion Wei Qi monthly physiological change might relate to lipid metabolism and amino acid metabolism closely and it might be influenced by change of hormone level.