Abstract: 15 samples of geosynthetic-encased stone columns (GESCs) with a dimension of ϕ300 mm×600 mm and degree of compaction of 0.9 are made using three types of fills of crushed stone, pebble and sand and five different strength woven sleeves made of polypropylene geotextiles. The uniaxial compression tests are performed on the samples to investigate the characteristics of strength of GESCs. The results show that different failure modes happen to the GESC body with different fills under uniaxial compression. The crushed stone can partly puncture the woven sleeves to produce obvious holes and pebble is extruded to break the transverse polypropylene slices, while the longitudinal slices are separated. The sand evenly breaks the transverse slices with no obvious holes on sleeves. The strength of the GESC body has a positive relationship with the strength of the sleeves and the fills. The stress-strain curve of GESC body at preliminary loading stage is mildly concave down due to the initial densification, then increases linearly up to the peak stress, and subsequently decreases, showing strain-softening characteristics. Based on the present data and those of uniaxial and triaxial compression tests carried out by the authors before, the theoretical formula for the strength of the GESC body is amended, and the results of the modified formulas are proved to be in good agreement with the experimental ones.