This paper researches the feasibility of liquid fermentation of Pleurotus ostreatus strain to produce xylanase using brewer's spent grain as raw materials.The best medium formula was obtained by orthogonal experiment.The important indicators(reducing sugar and xylanase) on different fermentation time was also obtained.The results are as follow:the optimum medium formula of beer's spent grains 6g,soybean meal 0.32 g,corn flour 2 g,sugar 10 g,pH 5.0.The best time for fermentation was 72 h.Under this condition...