The invention relates to a wafer bonding method for improving bonding strength. The method comprises steps that, two to-be-bonded wafers are provided and are respectively a first wafer and a second wafer; a first silicon dioxide film is formed on the surface of the first wafer through deposition, and a thermal oxide layer is formed on the surface of the second wafer through thermal oxidization treatment; a second silicon-enriched silicon dioxide film is formed on the first silicon dioxide film through deposition and planarization treatment, unsaturated bonded silicon atoms are distributed on the first silicon dioxide film and the second silicon dioxide film respectively, and concentration of the unsaturated bonded silicon atoms on the second silicon dioxide film is higher than concentration of the unsaturated bonded silicon atoms on the first silicon dioxide film; the second silicon dioxide film of the first wafer contacts with the thermal oxide layer of the second wafer for bonding. Through the method, wafer bonding strength is improved, and crack on a wafer bonding interface in a packaging process is prevented.