The logical algebra (Boolean algebra)has been widely used in a number of technical branchs. It is a pity that its application in earthquake prediction seems rare. So far as the research method on earthquake prediction is concerned, related to seismicity and its mechanical trigger factor is both quite widespread and noticeable, but it is still very difficult to apply the results obtained from abovementioned research concretely to earthquake prediction, because of the inregularity and complication in seismicity. The author tries to improve the results of abovementioned research by introducing the method of logical algebra. For this purpose, the general method for logical function which is adequate for earthquake prediction has been studied in this paper. As an instance for applying this method, selection 12 predicting foctors which consist of solar activities and seismicity on a global scale by means of the data in the period of A. D. 1914-1973, the predicting equation for logical algebra function to judge the annual strong earthquake hazard in continental crust in Gansu, Ningxia, Qinghai and Xinjiang of north-west China with magnitude M_s≥7 has been constructed. The historical coincident percentage for this equation in A. D. 1914-1973 is 100%, and the coincident percentage of the text of extrapolation in A. D. 1974-1982 is 88.9%, and this equation is useful for judging large background on annual earthquake situation in the abovementioned regions, This research indicates that the method of logical algebra function is one of hopeful methods concerning integrated earthquake prediction.