Experiment was conducted to study the effects of Bromus riparius on soil and water conservation on the slope with calcareous cinnamon soil in Beijing by analyzing the relation to main biological characters and soil and water loss for a year.Bromus riparius turned green in April and its cover was over 85% in July.In August,their overground and underground biomasses at the highest plant density were 2 322.6 and 5 623.0 kg/hm²,respectively,and the root amount in 0? 10 cm soil layer was important to prevent soil and water loss.T he main form of soil erosion on the slope with the calcareous cinnamon soil in Beijing was surface runoff.Rainfall and biological characters were two major factors to soil erosion on the slope.T he order of factors was surface runoff> rainfall> rainfall intensity> slope degree> vegetation cover> vegetation height> tiller density according to their effects to soil erosion.After one year Bromus rip arius,the physical properties of the calcareous cinnamon soil were significantly improved.Soil bulk density was deduced by 2.4% ~ 9.8%,soil compaction was decreased,and infiltration capacity was promoted.T he yearly amount of surface runoff loss and soil erosion modulus on the slope were reduced to 13.5 mm and 105.2 t/(km²? a) and the capacity of soil and water conservation reached 65.4 % and 98.1%,respectively.Grass planting on the slope with the calcareous cinnamon soil has great significance in soil and water conservation.