The invention discloses a decorative integrated light load-bearing heat preservation wallboard and a preparation method thereof. The decorative integrated light load-bearing heat preservation wallboard comprises a magnesium-based cement foaming layer, a magnesium-based cement fiber material surface layer I, a steel wire mesh layer I, a steel wire mesh layer II, left C-shaped steel, right C-shaped steel and a magnesium-based cement fiber material surface layer II, wherein the steel wire mesh layer I and the steel wire mesh layer II are respectively located in the magnesium-based cement foaming layer; the steel wire mesh layer I is located at the upper part in the magnesium-based cement foaming layer. The preparation method of the decorative integrated light load-bearing heat preservation wallboard comprises the following steps: (a) preparing a magnesium-based cement foaming material; (b) preparing a magnesium-based cement fiber material; (3) preparing a lower magnesium-based cement fiber material; (d) conveying to a foaming zone by using a conveyor belt; (e) preparing the magnesium-based cement foaming layer; (f) preparing the magnesium-based cement fiber material surface layer I. According to the decorative integrated light load-bearing heat preservation wallboard prepared by the method, the preparation route is simple, energy conservation, environment protection and waste utilization are realized, needed raw materials are cheap and easy to obtain, and a product has lower production cost.