A novel cationic gemini surfactant was prepared by chlorination and quaternization in this paper. The target product was successfully synthesized, which was confirmed by infrared (IR) spectrometer and NMR analysis. Different methods including zeta potential determination, scanning electron microscope, IR, sessile drop method and spontaneous imbibition were used to investigate the mechanism of the wettability alteration of the oil-wet surface by the synthesized gemini surfactant (GABEO) in this work. Results show that the gemini surfactant has excellent surface activity (32.5 mN/m). Ion pair formation is responsible for the mechanisms of wettability alteration of the oil-wet sandstone surface by GABEO, dodecyltrimethylammonium bromide (DTAB), and didodecyltrimethylammonium bromide (GDTAB). Owing to better wettability alteration ability of the synthesized gemini surfactant, there are fewer asphaltene particles on the solid surface treated with GABEO. Compared with DTAB and the traditional gemini surfactant GDTAB, a lower balanced contact angle was obtained for GABEO due to the stronger ion pair desorption capacity; that is, GABEO has a stronger ability to change the wettability of the oil-wet sandstone surface. In addition, owing to the strongest ability to change the surface wettability, the core has the largest ultimate imbibition recovery among the three systems when GABEO is used.