Abstract: Climate monitoring and diagnosis is an important method to know about the changes of climate system and their causes, playing an important role in climate operation. The history and current status of the climate monitoring and diagnosis operation in China are reviewed and some new technologies, methods and mechanisms developed and applied in operation in recent years are introduced.In 1990, the operational system of monthly climate monitoring is established in China for the first time. After the developments of more than 20 years, the climate monitoring and diagnosis operation in China makes great progresses in the aspects of theory, method, technology, and operational system, which go through the stages from the simple analysis of station observations to the monitoring of the multiple layers of climate system and the dynamic diagnosis of climate anomalies.At present, a set of climate monitoring and diagnosis operation system on multiple temporal and spatial-scales is set up and continuously improved, and some new theories, technologies, and approaches are promoted and applied. In the aspect of atmospheric circulation, besides basic characteristic variables related to height, wind and so on, the monitoring and diagnosis operational products of stratospheric process, northeast cold vortex, Walker circulation, Hadley circulation, water vapor transportation are also developed. Furthermore, the monitoring and diagnosis operation of the extreme weather and climate events over China and the world is gradually set up and improved. In the aspect of ocean, besides the physical system in the tropical and extra-tropical ocean and atmosphere related to ENSO, the monitoring and diagnosis technologies and products in light of the sea temperature anomalies of Indian Ocean and Atlantic Ocean with the major modes of oceanic and atmospheric system are developed. In the aspect of sea ice and snow, the monitoring and diagnosis technologies and products of the Antarctic and Arctic sea ice concentration and days as well as snow days, snow areas, and snow depths of the Northern Hemisphere and China are developed and set up. In the aspect of land surface, the monitoring technologies and products on the basis of station observations of soil temperature and humidity are developed. At the same time, the research is enhanced on the key factors, such as atmosphere, ocean, land surface, sea ice, snow and so on, as well as the mechanisms how they influence climate anomalies in China.