| This paper use the NCEP/NCAR day-to-day reanalysis data of 500hPa high field and so on, choose Ural mountain, Baikal, Okhotsk as the key district, the mid-high latitude of Eurasia circulation courses that have long duration (scale of time is middle, namely during 10-30 day), maybe continue continuously after being intermittence of 1-2 days in middle, appear repeatedly is for research object, define an index "I" of the circulation pattern over mid-high latitude of Eurasia. A method is proposed to identify the summer typical persistent circulation pattern at 500hPa levels over Eurasia mid-high latitude. The climate characteristics of those typical persistent circulation patterns are studied. The decadal variance of the circulation pattern index "I" and precipitation field, heat field, sea surface temperature, etc. corresponding to different stage, different circulation pattern are analyzed. The main conclusion is as follows:1. It is well to identify the summer typical persistent circulation pattern at 500hPa levels over Eurasia mid-high latitude base on the circulation pattern index "I". The index have rationality and applicable value.2. From 1959 to 2000, the occurrence frequency of summer typical persistent circulation pattern E is about equal to that of type C, and the occurrence frequency of type W is relatively less; the occurrence frequency of pattern E and C's course is most high in June; the course of pattern E and C exist certain decadal variance or phased characteristic. During the course of pattern E and C, not only in Eurasia mid-high latitude but also in other areas of Northern Hemisphere have the circulation obvious differences. The occurrence of the summer persistent circulation pattern relates to the circulation of other area of Northern Hemisphere mid-high latitude, and there are obvious relevant relations too in other areas of the South and Northern Hemisphere. During the lasting course oftype E, 850hPa, 500hPa and 200hPa wind field is obviously different from that during the lasting course of type C. The same is true of the precipitation deviation distribution of China, and during type E course the monthly precipitation deviation is positive over the Yangtse River and Huaihe River basin and negative over North China .The situation of type C is opposite.The result is mainly to reflect the situation in June.3. The summer typical persistent circulation patterns over Eurasia mid-high latitude have obvious decadal variance: the occurrence frequency of Type C course is relatively high from the 1960s to the 1970s, and the occurrence frequency of type E course increased while the type C course has not appeared in the 1980s, and two kinds of course were about equal frequently in the 1990s. Namely there were obvious turns around 1980. From monthly situation watch, the situation in June and in August is respectively most similar and dissimilar to that of whole summer. There are certain relations between Circulation pattern index's decadal variance characteristic and decadal variation tendency of the precipitation of China: in the 1960s and the 1970s, in which the negative index are relatively more, the precipitation are abundant, and in 1980s in which positive index dominant the precipitation over North China are obvious deficient; The situation of the Yangtse River and Huaihe River basin is opposite. East Asia summer monsoon index have the same decadal variance as the circulation pattern index "I" and its magnitude have transition at the beginning in the 1980s.4. For different summer persistent circulation patterns over Eurasia mid-high latitude, their background heat field have difference. The composite analysis to the SST indicate the decadal variance of the summer persistent circulation patterns over Eurasia mid-high latitude and that of SST have close relation. It is obvious that external source force's function to the decadal variance of the summer persistent circulation patterns over Eurasia mid-high latitude can't be ignored.
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