Based on the polyester welded biaxial geogrid (PET25-25), different forms of geogrid were designed, such as uniaxial, biaxial, triaxial and multiaxial ones. By means of triaxial compression tests, the strength property and failure modes of these forms were obtained. Besides, the influence of the space between transverse ribs in uniaxial geogrid on the strength and the configuration of reinforcement inside the basic geogrid element were studied. It can be seen from the test results that different forms of geogrid had different reinforcing effects; the multiaxial geogrid had the best reinforcing effect, consuming the greatest amount of material, 2.21 times of the basic geogrid element; biaxial geogrids performed better in reinforcing than uniaxial and triaxial ones; the comparison of uniaxial geogrids and triaxial ones were different in different confining pressures, that is, in low confining pressure, uniaxial geogrids performed better than triaxial ones, in contrast, in high confining pressure, triaxial ones did better. In addition, the reinforcing effect of uniaxial geogrids increased with the space of transverse rib decreasing; uniaxial geogrids mainly improved the cohesion of reinforced sand, however, other forms of geogrid mainly increased the friction angle.