Abstract: In order to determine the photo-stability of trichodermin and its major degradation products, a series of photocatalytic degradation methods were used, including visible light, ultraviolet light, nano-titanium dioxide and ultraviolet plus nano-titanium dioxide. The major degradation products were confirmed using high performance liquid chromatography-mass spectrometry method, compared with some synthesized trichodermin derivatives. The possible reasons that the activity of degradation products decreased or inactivated were investigated. The results showed that when used alone, the visible light, ultraviolet or nano titanium dioxide had little effects on the degradation of trichodermin. However, ultraviolet plus nano-titanium dioxide was efficient in the degradation of trichodermin. It's found that the primary products of degradation were the trichodermin derivatives of trichomermol, 12,13-dyhydroxyl trichodermin(M-1), (12-H,13-OH)-trichodermin (M-2) and (12-H,13-OH)-trichodermol(M-3). In conclusion, trichodermin has high photostability, and ultraviolet plus nano-titanium dioxide were efective in degrading the trichodermin. Disruption of the key groups of inhibition protein synthesis in trichodermin may result in decreasing even inactivating the activity of the degradation products.