The invention relates to an aluminium oxide ceramic substrate, and a preparation method and application thereof. The preparation method of the aluminium oxide ceramic substrate comprises the followingsteps: mixing aluminium oxide powder, organic monomers, a cross-linking agent, an auxiliary agent and deionized water to obtain the slurry with the volume percentage of 40 to 44 percent, wherein themedian particle diameters of the aluminium oxide powder is 0.1 to 0.3 micron and the specific surface area is 7 to 10 m<2>/g; adding a catalyst and an initiating agent into the slurry; then, performing injection moulding to obtain a green body; drying the green body; then sealing the green body in vacuum; performing cold isostatic pressing treatment; performing glue removing and sintering on the green body in sequence to obtain the aluminium oxide ceramic substrate. According to the preparation method for the aluminium oxide ceramic substrate, the aluminium oxide ceramic substrate with high density, high heat conductivity, high dielectric strength, high mechanical strength, low thermal expansion coefficient and high purity can be obtained at a low sintering temperature.