The invention discloses hot-dip zinc-aluminum-magnesium coating high-strength steel and a preparation method and application thereof. The hot-dip zinc-aluminum-magnesium coating high-strength steel comprises a base material and a zinc-aluminum-magnesium alloy coating on the surface of the base material, and through component design and the control of a production process on the basis of the component design, a process production scheme and a core production technology, with a CSP thin slab continuous casting continuous rolling production line and a common hot galvanizing production line as thecore, of smelting, hot rolling, cold rolling and annealing are formed. According to the hot-dip zinc-aluminum-magnesium coating high-strength steel, the yield strength is greater than 550 MPa, the elongation is greater than 17%, and the hot-dip zinc-aluminum-magnesium coating high-strength steel is suitable for high-corrosion-resistant industries such as photovoltaic brackets and highway guardrails.