Growth of the natural ice-plate, including the ice-rampart, one of the particular phenomena on the freezing process, has been observed on the rivers in North Manchuria. Experimental equation of ice-thickness has been derived as H=2.32√u√T; H means ice-thickness, U means the mean values of air-temperature and T means the number of days. The curves of ice-thickness about the rivers of North Manchuria, referring the statistics of air-temperature, are figured and compared with the actually measured value of ice-thickness.