A composite index system for landscape evaluation of ornamental grasses was built from the aspects of ecological constraints, resources requirement and aesthetic values, and the ornamental grass landscapes in Beijing Botanical Garden and in Nanzhongzhou public green spaces were evaluated by fuzzy synthetic assessment (FSA) method. The results showed that the scores of "very apt" for the ornamental grasses in Beijing Botanical Garden and in Nanzhongzhou public green spaces were 0.459 and 0.413, respectively, while those of "apt" for the two landscapes were 0.302 and 0.301, respectively. The evaluation results were consistent with the public feedbacks, suggesting that the composite index system and FSA method were applicable for the landscape evaluation of ornamental grasses.