Alpine grassland is an important component of the ecosystem of Qinghai-Tibet Plateau,however,significant changes have occurred on species diversity and biomass of grassland across the elevation gradient in this region due to anthropogenic interference and climate change.Consequently,a field survey was conducted in a representative mountain in Luoma Town,Naqu City,northern Tibetan Plateau,in August 2018,to discover the impact of elevation gradient on species diversity and above-ground biomass and reveal their relationship with alpine grassland communities by exploring the quadrat method.Results showed that the plant coverage and above-ground biomass of alpine grassland decreased linearly with the increase of altitude observation of two variants decreased from 89.0% and 64.7 g·m~(-2) at 4 600 m to 67.3% and 41.8 g·m~(-2) at 4 800 m,respectively.Furthermore,remarkable differences existed among species composition of various elevation gradient and the xerophytic grasses species gradually replaced by the hygrophilous plants in the high elevation gradient.Additionally,both of the index of species richness and Shannon-Wiener was presented in an unimodal distribution pattern with the increase of altitude,whirst the E.Pielou index exhibited a U-shaped pattern.Last but not least,negative quadratic relationship existed between the above-ground biomass and the index of species richness and Shannon-Wiener,while,with the augment of elevation gradient,above-ground biomass exhibited a trend of increase and decrease with soil temperature and soil moisture,respectively.The findings of our study indicate that significant difference of vertical distribution of species diversity and biomass in north Tibetan Plateau as affected by elevation gradient,and moreover,there is important impact of temperature and moisture of soil on species diversity and biomass with different altitude.