A wafer thinning method and a wafer structure are provided. In the wafer thinning method, a to-be-thinned wafer is provided, and the to-be-thinned wafer is grinded on a rear surface of the to-be-thinned wafer. Then, a first planarization process is performed on a rear surface of the grinded wafer to restore surface flatness of the grinded wafer, and a second planarization process is performed on a rear surface of the wafer obtained after the first planarization process is performed until a target thinned thickness is reached.