A systematic method for the estimation of stability of valtrate was established.HPLC-electrospray tandem mass spectrometry(HPLC-ESI MS/MS) was applied to separate the degradation products of valtrate and identify structures of the main degradation products.The samples were separated on an Agilent Extend-C18 by gradient elution using acetonitrile-0.25% acetic acid as mobile phase and analyzed under positive ion mode.Four degradation products were identified with the parent nucleus structures of baldrinals-compounds,in which one of oxidation products was identified through the reference substance.An HPLC method was established for the determination of the content change of valtrate in H2O2 at different time points.The result indicated that the content change of valtrate in H2O2 fits the first order kinetic equation，and the degradation of 10% prototype product occurred in 0.5 h.This paper revealed the degradation mechanism and degradation rule of valtrate from two aspects of both qualitative and quantitative analysis,and provided a theoretical basis for further research.