The invention relates to a method for improving coal ash melting temperature by utilizing aluminium oxide as an additive, which comprises the following steps of: 1, sampling the required raw material coal to obtain a coal sample, grinding the coal sample until the granularity is lower than 60 meshes, and ashing to obtain a standard coal ash sample; 2, testing the ash melting temperature of a standard coal ash sample; 3, uniformly mixing the standard coal sample and the aluminium oxide in a mass ratio of 99:1 into a mixture, testing the ash melting temperature of the coal ash sample to be tested, and comparing with the ash melting temperature of the standard coal ash sample in the step 2; 4, increasing the mass ratio of the aluminium oxide in the step 3 by 0.2 percent, testing the ash melting temperature of the coal ash sample to be tested, and comparing with the ash melting temperature of the coal ash sample tested in the step 3; and 5, determining a mass ratio range of the aluminium oxide additive. The method has the advantages of reducing the slag formation of boilers burning Shenhua coal, and not corroding metal parts of the boilers.