Abstract: The partial degradation of Ulva polysaccharide were carried out by sulfuric acid degradation.Taking 50% as the target degradation rate,the key effects on partial degradation of Ulva polysaccharide were discussed.Their partial degradation master technological conditions were optimized by the response surface method.The results showed the optimized partial degradation technological conditions of Ulva polysaccharide were as follows:the concentration of sulfuric acid solution was 0.30 mol/L,degradation temperature was 95℃,polysaccharide concentration was 0.70%,degradation time was 1.0 h.Under the optimal conditions,the degradation rate of the Ulva polysaccharide was 50.94%.