In order to clarify soil erosion of degraded alpine meadow

the degraded grassland of Henan County in source area of the Yellow River was chosen as research object. Field rainfall simulation experiment in situ was adopted to analyzed the changes of soil runoff and erosion quantity with soil slope

degradation degree

rainfall duration and rainfall intensity under different rainfall conditions. The results showed that: Natural water content and density of degraded meadow soil declined with the slope and the degradation degree（P<0.05）. Under the same conditions

the runoff and sediment yields had negative correlations with vegetation coverage

showing power(y=140.69x-0.4667，R2=0.9882) and exponential functions (y=4294.3e-0.0418x，R2=0.9907) respectively. Both runoff and sediment yields had positive correlations with rainfall intensity

the correlation functions were y=40.35e0.0252x (R2=0.9708) and y=62.657e0.0201x (R2=0.9688) respectively. The plot runoff of 30° slope increased by 3.6 times and 1.7 times respectively than 10° and 20° slope

and sediments also increased by 16 times and 1.4 times respectively. These showed that the runoff and sediment yields increased sharply with the increase of slope. The variations of runoff and sediment concentrations were large under the vegetation coverage of less than 40%. Surface slope runoff began to rise slowly after 30 min of rainfall

and the slope sediment loss mainly concentrated in 5 ~ 15 min after rainfall

and the sediment yield was sharply reduced after 55 ~ 60 min of rainfall. Thus

it could be concluded that rainfall duration of one hour was the sensitive period of soil particle erosion. The confluence scouring of hillslope after natural slope runoff was the important reason of aggravate soil erosion in degraded grassland.