The invention relates to organic chemical synthesis. In order to solve the problem of lower storage stability of the product when the R/Si ratio of the organic silicon resin adhesive is lower, the invention provides a preparation method of an organic silicon resin adhesive, which comprises the following steps: adding tetraethyl orthosilicate, methyltriethoxysilane, dimethyldiethoxysilane and toluene into a reaction kettle, heating to 50-70 DEG C, adding a catalyst, dropwisely adding deionized water at 50-70 DEG C within 1-2 hours to perform hydrolysis, reacting for 2-4 hours, filtering out the catalyst, drying the liquid by distillation, heating the system to 105-115 DEG C to react for 5-10 minutes, adding a solvent for dissolution, cooling to room temperature, and blending with the solvent to obtain the organic silicon resin adhesive of which the solid content is 30-55%. The R/Si ratio in the organic silicon resin adhesive is smaller than 1; the storage stability of the product is enhanced; and the organic silicon resin adhesive is applicable to mica binding.