Abstract: Snowcover information is very crucial to ecological research，water resource evaluation and disaster prevention for 40%-60% surface of the northern hemisphere covered by snowcover. Monitoring of the snowcover extent has been a hotspot in snowcover studies. MODIS sensor provides daily snowcover products with high temporal resolution，using snow and ice index （NDSI） and classification threshold，but most of these products are disturbed by the clouds that are very common in the alpine areas. The passive microwave remote sensing，AMSR-E，provides daily snowcover products without clouds disturbance，however，the spatial resolution of AMSR-E products are very coarse with 25 km. So the aim of this study is to explore the method to combine the product of MODIS and the AMSR-E and to get the accurate and high special resolution snowcover products. To achieve this purpose，firstly，MOYD data were obtained by combing MODIS snowcover products （i.e.，MOD10A1and MYD10A1） at different transit time in a day，which came from MODIS sensors in TERRA and AQUA satellites. Secondly，MODAM data were derived by combining MOYD and AMSR-E. Lastly，the snowcover depth data observed in 26 weather stations in the Qilian Mountains area were used to test the accuracy of the snowcover products. The results show that the combination of MOD and MYD can reduce the clouds by 15%，while for the MOYD and AMSR-E；this value can be 100%. The results also show that this combination method can improve the classification accuracy of snowcover; the accuracy of snowcover classification of MOYD data is 24% and the overall classification accuracy is 59%. For the MODAM data，the accuracy of snow classification can get to 88% and the overall classification accuracy is 80%. The analysis of the temporal distribution of snowcover in the Qilian Mountains shows that the peak season of snowcover，almost 75% area of the Qilian Mountains is covered by snowcover，from the beginning of January to the late February because of low temperature and the large amounts of snowfall in this period. Through assessing of the uncertainty of snowcover product，the paper finds that the combination of remote sensing products from different time and different remote sensor is very effective in monitoring of the snowcover distribution.

Key words: snowcover monitoring, the Qilian Mountains area, MODIS, AMSR-E, snowcover