An external insulation wall having grid-reinforced insulation board anchored with mechanical devices includes: a base course wall (1), wherein a leveling and bonding layer (2), grid-reinforced insulation boards (3), plastic expansion anchor bolts (4), a thin plaster protecting layer (5), and a finishing layer (6) are provided on the base course wall (1) from inside to outside in turn. Holes are dilled on the grid-reinforced insulation boards (3), and the grid-reinforced insulation boards (3) are directly fixed on the base course wall with the plastic expansion anchor bolts (4), in such a manner that all load of an external insulation system is born by the plastic expansion anchor bolts (4), and the plastic expansion anchor bolts (4) transmits the load to the base course wall (1). The external insulation wall can solve technical problems of low bearing capacity and difficult surface treatment caused by an old base course wall.