Abstract: Oak woods, pure or mixed, are the most common wooded formations in Sardinia covering over 20% of Sardinian territory. They have a very high environmental and economic value thanks because of the cork production and their inclusion as pasture in livestock farming system. Numerous studies were conducted on the relationship between forest preservation and pasture management have showed the compatibility of a moderate cattle grazing with the forest conservation. However, researches focused on the grazing effect on forest biodiversity are still insufficient. The aims of this work were to evaluate the relationship between cattle grazing in a silvo-pastoral system and forestry conservation and to analyse its influence on flora biodiversity. The research was carried out between 2011 and 2015 at the experimental oak forest of Agris Sardegna, located in the North-West of Sardinia. Inside the experimental oak forest covering about 70 ha and dominated by Downy Oak (Quercus pubescens L.), were identified 5 circular sample areas (1256 m2), representative of the total areas. Within each circular area the botanical species composition of the herbaceous sward was established and the diameter and height of trees were performed. This study was conducted annually, in June, according to the phytopastoral method of Daget and Poissonet (1971). A total number of species and their abundance was determined. The grazing value and the indices Piélou’s evenness, Shannon-Wiener for the biodiversity were assessed. The results seem to confirm low intensity cattle grazing compatibility with the maintenance of forest cover and botanic biodiversity.