The invention relates to alkalescence polishing liquid for a ruthenium blocking layer and a preparation method of the liquid. The polishing liquid is prepared from, by weight, 1-5% of silica sol, 0.5-5% of ethylenediaminetetraacetic acid tetra(tetrahydroxyethyl-ethylene diamine), 0.5-4% of hydrogen peroxide, 0.1-10% of non-ionic boundary surface active agent and the balance deionized water. The pH value of the alkalescence polishing liquid is 9-13. The polishing liquid can make Ru and Cu reach a high polishing rate, the chemical reaction is obviously enhanced in the polishing process, controllability is high, and Ru and Cu can have a good rate selection ratio; the galvanic corrosion of Ru and Cu in the polishing process is low, and the galvanic corrosion can be effectively restrained and reduced; surfaces are smooth and flat after being polished, global flatness is high, and roughness is low; pollution is small, reliability of equipment is improved, the equipment is still stable under the high pH value condition, and post-cleaning is easy.