Based on the daily 500 hPa geopotential height from realtime database of National Meteorogical Information Center, the Northern Hemisphere and key re gions blocking high monitoring and diagnostics technique which fits for operatio n was selected. Using the blocking high index, realtime blocking high monitori ng over each longitude at the midhigh latitudes in the Northern Hemisphere was achieved. Key regions in Okhotsk, Baika and Ural, which can affect on summer pre cipitations in China, were selected for blocking high monitoring. Meanwhile, dai ly and 5days running mean general circulation patterns of 500 hPa in the North ern Hemisphere were both monitored. Thus, the realtime operational system of m oni toring and diagnostics for the Northern Hemisphere blocking high was set up. Thr ough the analysis of blocking high monitoring products of 2006, the monitoring r esults accorded with the fact, including the blocking intense and location. These products were helpful for summer precipitation prediction of China.