In this paper precursory information is extracted from quasi-continuous geodetic data in Tang-shan area with slope-difference method

in which the deformation data are scaned over total time domain and calculation schemes are compared and selected. The statistical relation between the anomalies of the deformation and the earthquakes with magnitude ML≥5. 0 in Capital Circle

especially in Tangshan area is presented. Because the seismicities in different period arc different

scans are performed over different time spans after optimal schemes are selected. With the confidence level of 97. 5%

the test of R-value evaluation is made and the information extracted are significant. The results have shown that the earthquake activities in different period are different and relationships between slope-difference abnormal information and moderate-small earthquakes in the area are also different in different periods.