Abstract: The maximum magnitude, repetition rate and the magnitude-frequeney relation are Jjiven by G-R relation which are applied to long term corthquake prediction. Their effect and defects have been tested and analysed. The preliminary results are as followsi (1) The maximam magnitude is often overestimated by G-R relation, It would be better coincident with tht data by usinR revised G-R relation byUtsu(l978),(2)The repetition rate given by G-R relation in a seismically active period often makss higher or lower estimate for eismicity in the future 100 ycars. The uncertainty is several times to an order of magnitude, (8) The effects of the magnitudc-frcguency relation are not good.