Environmental biosafety is the key issue in the healthy development of the graphene industry, but the toxicity of graphene to moss is still unknown to date. Herein, we investigated the influence of graphene oxide (GO) on the growth, chlorophyll content and structure of white moss Leucobryum glaucum. Our results indicated that GO did not alter the fresh weight of L. glaucum, but inhibited the dry weight gain seriously, resulting in higher water-holding rates. GO induced the suppression of chlorophyll contents and up-regulated the chlorophyll a/b ratios, thus might influence the photosynthesis of L. glaucum. GO disturbed the microstructure and ultrastructure of L. glaucum at high concentrations, inducing the destruction of cell wall, the separation of cell wall and membrane, and the formation of micropores on the leave surface. GO led to the decrease of glutathione levels and catalase activities of L. glaucum, suggesting the existence of oxidative stress. Our results collectively suggested that graphene had the potential environmental risk to moss plants, and the release of graphene into the environment should be strictly restricted.