A preparation method for a ceramic composite material, a ceramic composite material, and a wavelength converter. The preparation method comprises: preparing an aluminium salt solution and a fluorescent powder; dispersing the fluorescent powder into a buffer solution having a pH 4.5-5.5 to obtain a suspension; titrating the suspension with the aluminium salt solution to obtain a fluorescent powder coated with Al2O3 hydrate film; calcining the fluorescent powder coated with Al2O3 hydrate film to obtain a Al2O3-coated fluorescent powder; mixing aluminium oxide powder with a particle size of 0.1 μm-1 μm and aluminium oxide powder with a particle size of 1 μm-10 μm to obtain mixed aluminium oxide powder; mixing the Al2O3-coated fluorescent powder and the mixed aluminium oxide powder to obtain mixed powder, the Al2O3-coated fluorescent powder being present in 40%-90% by weight of the mixed powder; and pre-pressing and sintering the mixed powder to obtain the ceramic composite material.