Slope maintenance and earth retaining structures are one of the most important topics in Geotechnical Engineering, especially in Hong Kong and Macau where the flat land are limited in both urban and suburban areas. Most of the methods of slope maintenance are not environmental friendly because of lacking the vegetations on the slopes. The lacking of the vegetations on the slopes would change the environment of the lives at the adjacent area and it would affect the current ecological system. The maintenance of non-environmentally green slopes is also very costly. The protection of slopes using Geofiber Technology with selected vegetation is environmental friendly and successful to provide long lasting green slopes with less maintenance. Slope stabilizing with Geofiber is a unique technique. Gcofiber, composite material of sand and fibers, was studied in the laboratory for its shear strength. Normally there are only two ingredients (sand and polyester fiber threads) in Geofiber. In this study, shear strength of both sand and reconstituted Geofiber was measured with direct shear apparatus (DSA). Initially, sand was tested with both conventional direct shear apparatus (CDSA) and modified direct shear apparatus (MDSA). Load pad and load pin are not fixed for CDSA but fixed for MDSA. Test results showed that MDSA is more favorable than CDSA. Therefore, only MDSA tests were carried out for shear strength tests of reconstituted Geofiber in this study. Shear strength increases in Geofiber is not only due to the friction between fibers and sand but also tensile strength of polyester fiber. Less than 2mm grain size of sand is suitable to test with CDSA that has an area of 100mm x 100mm for 20mm height of specimen. MDSA can test sand with more than 2mm grain size. Crushed granite coarse sand showed higher cohesion when tested with CDSA. It was because upper load pad rotated excessively and jammed with upper shear box, which in turn jammed with swan neck. These jams appeared as apparent cohesion of coarse sand. Dilation of specimen was less due to the jams. When tested with MDSA for Geofiber, there was no jam and load pad could go up freely. Therefore, less apparent cohesion was obtained and dilation of specimen was higher than the results of CDSA test. Laboratory test results showed that shear strength of “discontinuous fiber reinforced soil-fiber vertical orientation” (DFRS-V)is higher than “discontinuous fiber reinforced soil-fiber horizontal orientation"" (DFRS-H). Shear strength of “continuous fiber reinforced soil-fiber vertical orientation"" (CFRS-V) is higher than “continuous fiber reinforced soil-fiber horizontal orientation"" (CFRS-H). Shear strength of CFRS-H, CFRS-V, DFRS-V are higher than sand except DFRS-H, It seems that shear strength of CFRS is generally higher than DFRS, but DFRS-V shear strength is higher than CFRS-H. This is because higher numbers of polyester fibers perpendicularly presented at the shear zone. This means that when the more number of the fibers presented at the shear plane, the higher the shear strength of Geofiber. In vice-versa, the lesser numbers of the fibers presented at the shear plane, the lower the shear strength of Geofiber. Continuous fibers always give higher shear strength than discontinuous fibers. The higher numbers of continuous fibers perpendicularly passing through to the shear plane gives the highest shear strength. The study shows that understanding of the nature and concept of Geofiber is very important. Otherwise test specimens will not be representative and chosen shear direction may not be corrected. Non representative specimen and wrong shear direction were the common mistake to test for the shear strength of Geofiber.