To obtain the influence mechanism of epoxy resin content, curing time, and other external factors on the compressive strength and seawater corrosion resistance of geopolymer, the NaOH and Na2SiO3 were used as activators; the effect of epoxy resin concentration on the corrosion resistance of metakaolin-based geopolymer was investigated by experiments. The mechanism of epoxy resin concentration affecting the polymerization process and the properties of geopolymer was analyzed by X-ray diffraction, scanning electron microscopy-energy spectrum, and Fourier transform infrared spectroscopy. It was shown that the epoxy resin slowed down the polymerization. The presence of epoxy resin had a beneficial effect on compact structure. Furthermore, compared with the noncorrosive specimen, mixed with 30% specimen’s average compressive strength increased by 4.77MPa and 4.24MPa after curing for 1d and 3d and soaking for 56d.