Abstract: The mechanical breakup of ice covers during spring often lead to the serious ice-dam formation.However,the method for predicting the ice-cover breakup based upon the mechanical principle is in short supply.In this paper with the mechanical-analysis methodology the mechanism of the longitudinal-crack formation during the river-ice initial breakup is fully investigated by using the theory of beams on elastic foundation.A theoretical expression for predicting ice-cover breakup is presented.The comparison with the field observations indicates that the presented formula can to predict the location accurately.