Abstract: Drought disaster in North China occurs frequently, it is one of the areas in China where drought extended widest, its intensity was most serious and lasting time was longest. In particular, in recent years, the serious drought extremely threatens agriculture, thereby economics, ecology and even daily life of people were impacted. Therefore it is important to find the causes of the persistent drought in North China, and identify the prior signal of drought degree and its lasting time. In this paper, the characteristics of circulation and ocean variation during dry and wet periods over North China are analyzed by using composition anomaly. The inter-decade tendency changes of 500 hPa height and sea surface temperature (SST) in North Pacific have great influence on Continued drought since 1980s. The results show that there were the correlations between the anomaly drought over North China and the tendency changes of westerly circulation and subtropical high. Based on signal-noise ratio the previous stronger signals of 3 severe drought events are discriminated from 500 hPa height field and SST field. The meaning of the stronger signal-noise ratio is that the remarkable difference between the recent atmospheric and oceanic anomaly and the multi-year mean occurred. For example, there were some antecedent strong signals before the summer drought in 1999, such as typical high control pattern in East Asia circulation, long lasting SST increasing abnormally over Kuroshio and Nino 4. Though the location and strength of the stronger signals before occurring of severe drought event are not all the same, the anomaly variations of the height nearby Ural Mountains and Bajkal Lake and the SST nearby Kuroshio, warm pool and Nino 4 region are important previous stronger signals.