The invention relates to a spiral pipeline inner wall grinding and polishing robot suitable for different pipe diameters, and belongs to the field of pipeline robots. A hub assembly and a cross-axis universal joint are mounted in a spline fit manner, three driving wheel grinding assemblies are arranged, two ends of drive shafts of the assemblies and a drive shaft support in the hub assembly are mounted in a matched manner through bearings, a motor and control and power assembly is mounted on a direction keeping mechanism, and a motor shaft of the assembly and the cross-axis universal joint are mounted in a spline fit manner. The spiral angles of the grinding assemblies relative to the cross section of a pipe fitting are adjusted in a self-adaptation manner, and therefore the aim that the position with the small pipe diameter and many impurities is ground much, and the position with the large pipe diameter and few impurities is ground little is achieved, the robot can be matched with multiple different-size grinding assemblies for use, the aim that one robot has multiple purposes is achieved, and the cost can be saved to a certain degree.