Abstract: A kind of clay modified by Cetyltrimethyl Ammonium Ahloride(CTAC) was prepared to solve the problem of sand fixation in desert highway construction and maintenance. H1, H2, H3, H4 and H5 were assigned to the treatments with mass ratios of CTAC to clay 2:4, 3:4, 4:4, 5:4 and 6:4, respectively. In addition, unmodified clay was prepared as the control group H. Water retention performance was tested in an artificial climate box to simulate the desert climate. And the changes of mass and compressive strength were compared before and after ageing to test the anti-aging property. The grass planting experiment was conducted to analyze the effect of materials on germination rates. At last, the mechanism of sand fixation and water retention was analyzed by X-ray diffractometer, infrared spectrum analyzer and scanning electron microscope. The results showed that the water retention property was obviously improved with the increase of CTAC content. The moisture content of H5 and H4 were 27% and 23% respectively, while H1 was 7% on the 7th day, indicating the water retention performance of modified clay samples were gradually enhanced with the increase of CTAC content. In the compressive strength test, the strength of the unmodified clay group H was failed to measure due to the strength less than 0.1 MPa, while the strengths of the modified clay samples were significantly improved, and the strengths of the modified clay samples all met the standard requirements (no less than 1 MPa). Moreover, the strength of the modified clay increased with the increase of the content of CTAC, with the highest and higher strength of H5 and H4 (2.2 and 2.1MPa respectively), and the lowest strength of H1 (1.7 MPa). This indicated that CTAC could bond dispersed clay particles together to form a consolidation layer, and its strength could meet the requirements of mechanical construction. In the anti-aging performance test, after aging for 500 h, no obvious cracks were found on the surface of the samples, and the water retention performance decreased by less than 5%. The strength and mass loss rate of all the groups increased with aging time, and the higher the CTAC content, the higher the strength and mass loss rate. The strength loss rates of H4 and H5 were respectively 7.3% and 10.4%, and the mass loss rates of H4 and H5 were respectively 2.6% and 3.2% after 500 h of aging. The grass planting experiment showed the germination rate of the unmodified clay group (H) was only 7%, far below that of modified groups. With the increase of CTAC content, the germination rate of grass seeds gradually increased. The germination rate of the modified group H1 was 33%, and the highest germination rate was up to 47% (H4). But there was no more increase when CTAC content increase further, and the germination rate of H5 group was 41%. The microscopic analysis showed that CTAC could bond the loose clay particles together through intercalating effect. The clay gaps were turned into hydrophobicity, which resulted in the increase of the water transport resistance. So the modified clay had better sand-fixation and water-retention performance. However too much CTAC blocked the space of clay particles, the permeability of clay decreased, so the germination rate of H5 decreased. Although the compressive strength and water retention performance of H5 is slightly better than H4, as a kind of sand fixation material, the most important performance is the survival rate of seedlings. Therefore, under the premise that all other performances meet the standard requirements, H4 with the highest germination rate was selected as the best treatment scheme. The results could provide reference for the application of the modified sand-fixing materials.