A motor rotor includes a cylindrical housing, a positioning ring and a plurality of magnets. The cylindrical housing includes a plurality of securing holes. The positioning ring is disposed on the cylindrical housing. The positioning ring is disposed with a plurality of flexible ribs and a plurality of securing ribs disposed corresponding thereto. Each of the flexible ribs is radially pressable. The flexible ribs are disposed in the cylindrical housing, and each of the securing ribs is inserted in a respective corresponding one of the securing holes. The magnets are disposed in the cylindrical housing. Each of the magnets is clamped between the adjacent flexible ribs and is arranged annularly along an inner wall of the cylindrical housing, so as to facilitate assembly.