It has been one controversial issue on the regularity and predictability of social development and the resulting validity of historical social science in academic circles. Popper criticized severely Marx’s historical materialism on the regularity and the predictability of social development in his writings. Scholars has refuted this criticism in methodology，history and politics，but it need to be analyzed from the theory deeply. Based on the actual historical process of the social development，it helps to clarify Marx’s historical materialism which has been distorted and misinterpreted by Popper and restore its truth，and deepen the understanding of the regularity and the predictability of the social development that we comb and interpret Popper’s critique on Marx’s historical materialism again from the law，the trend and the forecasting of social development，and analyses objectively and evaluate scientifically.