The theory of self-organized critical phenomenon is used to do a deepgoing research in earthquake prediction.Based on the physical meaning of all the variables,their usability in seismic science is discussed.The critical point problem about increasing small or moderate events before a strong earthquake is studied.Both the critical probability and the threshold of the correlation length are quantified.The spatial evolution pattern is essentially a kind of quantitative seismicity distribution map and can give approximate prediction for the spatial position of a future earthquake.