Abstract: During the river-ice breakup, the longitudinal cracks near banks are firstly formed due to the runoff increase, resulting in the detachment of central part of ice cover from both banks.Subsequently, as a result of horizontal bending or vertical bending of ice cover the transverse cracks will be further formed, and the continuous icE-cover is finally fractured into floes with cerain sizes.Based upon the theory and calculation method of elastic-foundation, the mechanism of transversE-crack formation is fully investigated.By means of studying on the bending moment and bending stresses of ice cover, the analytical expressions of the crack-spacing due to both horizontal bending and vertical bending are presented, and validated with the field measurements.The study indicates that the transversE-crack spacing depends on the icE-cover width, thickness, bending strength and topography.