Abstract: A magnetic scrubber assembly and its design method for cleaning the wall-glass of an aquarium are provided. The center of gravity of the internal scrubbing component is designed underneath its the geometrically horizontal central axes. A product of length Lp from a center of gravity Pp of an internal scrubbing component to a lowest part and the center of gravity P of the internal scrubbing component is smaller than a product of a length Lf from equivalent function point Pf of buoyancy F such that the internal scrubbing component is received to its lowest part. This ensures that the internal scrubbing component can erect automatically after it is lied down. When the internal scrubbing component breaks away from the control of a hand-held scrubbing component, the internal scrubbing component can sink upright, and the magnetic scrubber assembly is restored to the normal operation condition.