The invention discloses a steel floating box anti-icing device suitable for a semi-submersible platform in a polar ice area. The steel floating box anti-icing device comprises a fixed platform which is fixed on pile legs, wherein multiple groups of hydraulic permanent-magnetic chuck lifting devices are arranged at the lower part of the fixed platform; anti-icing split steel floating box anti-icing bodies are arranged at the lower parts of the hydraulic permanent-magnetic chuck lifting devices respectively; and the side surfaces of the anti-icing split steel floating box anti-icing bodies are in a wedge shape. According to the steel floating box anti-icing device suitable for the semi-submersible platform in the polar ice area, an enclosed steel floating box generates buoyancy force by virtue of an internal filler and does not have strict requirements on the water tightness; the manufacturing difficulty of the steel floating box is lowered; the phenomenon that similar steel floating box which needs to be strictly enclosed in general sinks in the sea once the water tightness is damaged is avoided; and the reliability of the split steel floating box anti-icing bodies is further improved.