Direct shear test and unconfined compression test are conducted on geopolymer-reinforced soft soil specimens of different curing ages (7 d, 28 d, and 60 d). Ratio of geopolymer mass to soft and wet soil mass (hereinafter referred to as “the ratio”)is designed at three levels: 10%, 12%, and 14%. Results demonstrate that the strength of reinforced soil climbs with the increase of geopolymer dosage; while at a given geopolymer dosage, the strength of reinforced soil also increases with the elongation of curing age. The reinforcement effect is good when the ratio is 14%. Furthermore, the relation between microstructure and macro-properties of reinforced soil is analyzed based on SEM scanning and CT scanning. Results indicate that smaller structural porosity would result in higher strength. The results offer scientific basis for the application of geopolymer-reinforced soft soil inpractical engineering.