Preparation method of modified silane coupling agent

A preparation method of a modified silane coupling agent comprises: (1), dissolving mono-anhydride or tetracid dianhydride in glacial acetic acid, adding allylamine according to a molar ratio of the mono-anhydride or tetracid dianhydride to the allylamine being 1:1 or 1:2, stirring and reflowing for 3-24 h, adding water, filtering, washing, and drying to obtain an imide product; (2), dissolving the imide product in an aprotic solvent of medium polarity, adding 0.2 ml or 0.35 ml of a catalyst and trialkoxysilane according to a molar ratio to the imide product being 1:1 or 2:1, and reacting at 50-70 DEG C for 5-48 h, distilling at reduced pressure to remove a low-boiling-point fraction to obtain a product.Least catalyst is used at the premise of ensuring optimal catalytic efficiency so that lowest production cost is achieved.