Abstract: In order to develop a new and functional natural food additives，crude pigment obtained from the fermentation liquid of Trichoderma viride T-YY was treated with vacuum freeze-drying technology and its ultraviolet-visible spectroscopic properties and stability were studied. The results show that at least four kinds of yellow pigments with different properties are found in the crude pigment. The yellow pigments are easy to dissolve in water and methanol and the colour values are high. Each has one absorption peak of yellow pigments in ultraviolet range and visible range and the maximum absorption wavelength were 286.5 nm and 380 nm, respectively. The colour of the yellow pigments retains a good hue of bright yellow in far-ranging of pH value, the aqueous solution gets turbid when pH<5.0 and retains bright yellow when pH≥5.0 . It is relatively stable to light indoor when the pH value from 3.0 to 9.0 and heated at 100℃ for a short time. The antioxidation ability to H₂O₂ and HNO₃ is strong but it is sensitive to reductant. Fe³⁺、Cu²⁺ and Mn²⁺ can fade the colour of the yellow pigment, but Fe²⁺、Mg²⁺、Zn²⁺、Ca²⁺、K⁺、Na⁺ have a good protective effect on it. In a word, the yellow pigment from Trichoderma viride T-YY is worth to develop for its high stability.