The invention discloses a glass surface hydrophobic modifier. S-triazine is employed as a core, and peripheral end groups are six hydrophobic alkyl end groups and a coupling group, the structural formula is shown in the specification, R1 is an alkyl group with 4-12 carbon atoms, and R2 is a methyl group or an ethyl group. The synthetic method comprises the following steps: first, ingredient preparation is carried out; section, a reaction is carried out; third, 3-aminopropyl-triethoxysilane is added and a backflow reaction is carried out; fourth, organic solvents are removed, washing is carried out, and a glass surface hydrophobic modifier is obtained. The glass surface hydrophobic modifier employs cheap and easily available cyanuric chloride as a raw material, six alkyl chains are introduced as hydrophobic end groups and an organosiloxane is introduced as a coupling end group with glass successively, hydrophobic modification of glass surfaces can be carried out in simple conditions, the contact angle of water on the surface can reach more than 90 degrees, and good hydrophobicity and glass light transmittance are achieved. The synthetic method is advantaged by cheap raw materials, mild synthesis conditions, simple technology, high yield and good application prospect.