Abstract: Using monthly dynamic extended range forecast (DERF), the 500hPa geopotential height fields are evaluated with three kinds of scores. The skill of momthly DERF is generally better than that of persistence and climate forecast. The products of DERF can be used as a reference in prediction, but still do not meet the demands of the operational system. Further analyzing 500 hPa geopotential height, it is found that some circulation characteristics are well predicted, their forecasting skills are higher than that of 500 hPa. Some studying results and experiences show that there are better correlations between circulation characteristics and element forecast which could be used in operational prediction. This provides another way for interpretation of DERF Products.