The invention discloses a building outer wall compound insulation board and a mounting method thereof. Holes are densely preformed in a plane of the insulation board. Anchoring steel wires and steel wire mesh pieces are preinstalled in the holes, and high-grade slurry is injected into the holes to form handle bodies. Waterproof non-combustible materials which have good rigidity and are easily formed are adopted to make into a hole outer shell. If the plane size of the hole outer shell is large, cross bars can be additionally arranged inside the hole outer shell to enhance the rigidity of the hole outer shell. The insulation board and the outer shell are combined to form the dumbbell type dense compound insulation board. Holes do not need necessarily punching in a wall space. A steel wire mesh cement mortar insulation system and a thin plastered insulation system can be formed through adoption of the conventional construction technology. The insulation system can automatically form dense dumbbell type restraint pieces. An inner painting layer and an outer painting layer are fixed through the dumbbell type restraint pieces into a micro vertical flat slab system and are firmly cohered on a basic wall. Thermal insulation materials are locked in the shell. Consequently, durability, fireproof performance, earthquake resistant performance, waterproof performance and seepage-proof performance of the insulation system are greatly improved. Strength and stiffness of the system are larger than those of an existing insulation system. The dumbbell type dense compound insulation board is also suitable for roofs, floors and ground, provides a new scheme for inorganic insulation boards and soft, loose and molding insulation materials to better serve construction engineering and finds a new way for organic insulation boards.