Impacts of coal exploitation on grassland are grassland destruction and desertification.In this paper

the desertified grassland in Huolinhe open-cast coalmine was extracted from remote sensing imagey by using decision tree and back-propagation（BP） neural network

and the desertification during the past 16 years in the study area was analyzed.The results indicate that ① from 1987 to 2003

there is a strong to weak

then weak to strong evolution process for the total grassland desertification

which can be attributed to climate change and human activities

especially to the influence of climate change;② there is a evolution similar rocess from strong to weak

then from weak to strong for the area of medium desertification and slight desertification

which can be mainly ascribed to the climate changes

then to the over-grazing

uprooting of the medicinal materials

and over-reclamation;③ due to the coal exploitation

the severe desertification is always in shape of " ▲" around the mining land

and developed to the east quickly with the help of monsoon;④ the area of severe grassland desertification is on the increase during the past 16 years

and there is much correlation between the mining land and severe grassland desertification area

so the mining land area can be served as an important indicator for coalfield eco-environment assessment and prediction.