Abstract: Using big-leaf cassia in Etuoke Front Banner of Inner Mongolia as test materials and choosing Leymus chinensis and alfalfa as control, the nutritional value of big-leaf cassia was comprehensively assessed by conventional nutritional component analysis, in vitro gas production and fermentation test,two-stage in vitro digestibility test and nylon bag test, etc.. From the conventional nutritional component analysis, the protein content in big-leaf cassia with the height of 0.8-1.2 m was the highest, followed by alfalfa. From the fermentation parameters in vitro,there was no significant difference. From the digestibility in vitro,the protein digestibility of big-leaf cassia with the height of 0.8-1.2 m was lower than that of alfalfa and higher than that of L. chinensis and other two kinds of cassia. From the digestibility in semi-vivo , the protein digestibility of big-leaf cassia with the height of 0.8-1.2 m was lower than that of alfalfa and higher than that of other three kinds of feed. In conclusion, it was found that big-leaf cassia with the height of 0.8-1.2 m was not suitable as fiber feed but fibrous feed.