Based on remote sensing snow cover data in the Northern Hemisphere and surface observations for snow depth and days with snow cover in China,the monitoring and diagnosing methods for snow cover are studied. An operational system for snow cover in the Northern Hemisphere was set up. The operational products included spatial distribution for days with snow cover in the Northern Hemisphere,snow depth and days with snow cover in China,anomalies indices for snow area,and snow depth and days with snow cover in each region.