The invention discloses a build-up welding method of a turbine blade alloy layer, and belongs to the field of metal materials. A water atomization or gas atomization process is adopted for preparing abuild-up welding material, and the build-up welding material mainly comprise 35-39 wt% of Ni, 20-25 wt% of Cr, 0.5-0.6 wt% of C and the balance Fe. Main material powder with the granularity being 45-75 micrometers and W, Nb and Hf powder with the average granularity being 2-3 micrometers are screened and subjected to ball milling and mixing, and final build-up welding mixed powder is obtained; and then the build-up welding mixed powder is subjected to build-up welding at the position, most likely to be scoured by steam, of a blade through the laser cladding technology, the surface of the build-up welding layer is machined after build-up welding is completed, accordingly the build-up welding layer meets the dimension requirement of the blade, and the final blade with the alloy layer is obtained. By means of the laser cladding method, the alloy powder is subjected to build-up welding on the surface of the blade, interface bonding is better, and damage to the basic performance of the blade is small; and the water corrosion resisting performance of the blade is improved, and meanwhile the performance of the blade is not reduced.