A windshield wiper assembling structure for preventing loose attachment of a driven wiper arm assembles the driven wiper arm having a hook arm on a windshield wiper fixing stage. The windshield wiper assembling structure includes an assembling stage and a positioning stage. The assembling stage has a through groove, an elastic blocking slice, and a first fastening groove which is formed at one side edge of the elastic blocking slice. The first fastening groove fastens on the windshield wiper fixing stage. The assembling stage has a containing groove on a top surface thereof to accommodate the hook arm. The positioning stage has a cover cap and a positioning arm which is extended from the cover cap. The positioning arm has a second fastening groove corresponding to the first fastening groove. The second fastening groove fastens on the windshield wiper fixing stage and corresponding to the first fastening groove.