Abstract: Based on the theory of solid tide, this paper has proved the characteristics of vector of tilt spring tide observed during vernal equinox is an ellipse. Because during the spring tide of syzygy period also exists an ellipse, so the ellipse tidal factor may be calculated. The observations in Sichuan-Yunnan seismic experiment region and a nalysis results demonst rated that the anomalies of ellipse tidal factor are closely related to the strong earthquakes. The physical explanation of ellipse tidal factor has also been given.

Key words: ellipsetidal factor, Earthquake prediction, Correlation