The East Asian monsoon diagnostic and monitoring operational syste m was introduced, which is one of the important operational systems of National Cl imate Center. The atmospheric data, outgoing longwave radiation (OLR) data and China station precipitation data were received realtimely by this system. The system archived realtime monitoring for variation of rain belt over China and the activity of East Asia monsoon (including the break out, advance and intensi ty of summer monsoon, etc). The East Asia monsoon diagnostics and monitoring ope ration system provides multifold monitoring products, as well as the East Asia M onsoon monitoring bulletin.