3,3′,5,5′-tetramethyl-4,4′-biphenyl diglycidyl ether (TMBPDGE) modified waterborne acrylic resin with excellent water resistance and mechanical properties was synthesized by a homogeneous solution polymerization. Infrared analysis revealed that TMBPDGE could successfully participate in the synthesis. On this basis, the experimental conditions such as polymerization method, solid content, monomer addition method and curing temperature are optimized by using the results of immersion test, contact angle, tensile strength, elongation at break and hardness determination. The optimal amount of TMBPDGE is investigated and the resin is further characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The experimental results show that when the amount of TMBPDGE is 10 wt%, the water resistance and mechanical properties of the resin are greatly enhanced, and the cured resin film modified by TMBPDGE can withstand the soaking in water for more than 35 days, while that of film without modification is only one day. The tensile strength can reach 9.12 MPa, which is 2.2 times than that of the film without modification. Based on the enhanced properties, the modified resin provides a great potential in the fields of wood coatings, which require good water resistance and mechanical properties.