The invention discloses a method for determining silica in a silicon steel surface oxidation layer. A series of treatments such as electrolysis, acid melting, alkali wash are carried out on silicon steel to be determined to destroy or dissolve unstable oxide inclusions in anode residues so as to achieve the purpose of separating SiO2 and other oxide inclusions, then stable anode residues are put in a muffle furnace to be melted, after being cooled, the melted anode residues are leached with nitric acid, Si content is determined on an ICP (Inductively Coupled Plasma) spectrograph, and finally the content of SiO2 is obtained through conversion. The method disclosed by the invention is simple and feasible, the determined data is real and effective, the gap in the prior art is filled, and a trend is provided for improving the quality of oriented silicon steel.