Abstract: According to geological tectonics and seismic activites this paper devided North China ( 30- 45N, 105 - 130E) into four areas. We analized the Nouth China earthquake catalogue from 1970 to 1986 (from 1965 to 1986 for Hua Bei, the North China, plain region) and identified forty- two bursts of aftershock. Seven of them occurred in aftershock regions of strong earthquakes and seventeen of them in the seismic swarm regions. The relation between strong earthquakes with the remaining eighteen bursts of aftershocks has been studied and tested statistically in this paper. The result of statistical testing show that the random probability p of coincidence of bursts of aftershock with subsqeuent strong earthquakes is less than six percent. By Xu's R scoring method the efficacy of predicating strong earthquake from bursts of aftershock is estimated qreater than 39 percent.Following the method proposed in the paper we analyzed the earhtquake catalogue of China from 1987 to 1988-6 The results show that there was only one brust of aftershock occurred on Jan. 6,1988 with M=3.6 in Xiuyan of Northeast China. It implicates that a potential earthquake with Ms 5 might occur in one year afterwards in the region of Northeast China. Actually on Feb.25,1988 an earthquate with Ms= 5.3 occurred in Zhangwu of Northeast China. Another example is Datong-Yanggao shock on October -18, 1989 which is a burst of aftershock. Three hours after an expected shock with M=6.l took place in the same area. Two examples above have been tested in practical predication and this shows that bursts of aftershock are significant in predicating strong earthquakes.