Abstract: Hanjiang River Basin is the water source area of the Middle Route Project of South to North Water Diversion, and forest covers play an important role for the protection of ecological security at this place. In order to monitor the forest cover change of Hanjiang River Basin during 2007-2017, Google Earth Engine platform was used to deal with the Landsat multispectral images and ALOS (Advanced Land Observation Satellite）SAR data at the whole area. According to the regional characteristics, nine characteristic indexes were selected from both of the Landsat multi-spectral and ALSO SAR images, and random forest classification method was applied to extract the forest distribution in 2007 and 2017 for monitoring changes in forest cover in the Hanjiang River Basin. The results show that the overall accuracy of forest cover classification is 98.0% at 2007 and 98.6% at 2017, which is significantly higher than that of forest classification by using only Landsat multispectral data or ALOS SAR data. The forest cover area of Hanjiang River Basin increased by 5 653.21 km2 from 2007 to 2017. For the Xixia and Nanzhao of Henan Province and Danjiangkou Reservoirs, forest covers illustrated an increasing trend, while the forest covers around Jingmen City,Shiyan City and Hanzhong City showed a decreasing trend.