Abstract: Abstract : Background In the process of ecological restoration, natural, artificial and natural-synthetic soil amendments are widely used. Natural soil amendment biochar and humic acid and synthetic soil amendment polyacrylamide are commonly used as three kinds of soil amendments, which can improve the physical and chemical properties of soil in harsh environments such as cold and drought, and contribute to the growth of plants. The above three kinds of soil amendments have been widely studied and applied in the field of ecological restoration. Method In this study, three common soil amendments, biochar, humic acid and polyacrylamide, were set up according to the commonly used proportion of ecological restoration and the related research on the amount of three soil amendments. Different ratios were added to the soil, and the soil water retention rate under different ratios was tested. The internal friction angle and cohesion of the soil under freeze-thaw cycle conditions were analyzed to analyze the effects of different ratios of soil amendments on soil water retention and freeze-thaw resistance. ResultsThe results showed that: 1) Different combinations of soil amendments could increase the water retention performance of the soil to a certain extent, and the water retention performance increased by 128.72 % to 214.72 %; 2) The soil internal friction angle and soil cohesion under the condition of freeze-thaw cycles were used to characterize the anti-freeze-thaw effect of different combinations of soil amendments. The internal friction angle and cohesion of the soil amendment group were greater than those of the non-added group. The internal friction angle increased with the increase of the number of freeze-thaw cycles, from 1.04 times to 1.37 times, while the gap of soil cohesion was narrowing, but the gap was small, from 1.29 times to 1.10 times; 3) Through the TOPSIS method, it can be seen that different combinations of soil conditioners have different performance in water retention and freeze-thaw resistance. The ratio of better water retention performance is 3 % biochar (calculated by soil quality), 0.2 % humic acid (calculated by soil quality), and 0.005 % polyacrylamide (calculated by soil quality). For the anti-freeze-thaw effect, the ratio of soil conditioners is proposed from two aspects. Considering the internal friction angle, the best ratio of freeze-thaw resistance is 3 % biochar (calculated by soil quality), 0.3 % humic acid (calculated by soil quality), and 0.005 % polyacrylamide (calculated by soil quality). Considering the cohesion, the best ratio of freeze-thaw resistance is 2 % biochar (calculated by soil quality), 0.3 % humic acid (calculated by soil quality), and 0.01 % polyacrylamide (calculated by soil quality). Conclusion Therefore, through the water retention test and the determination of soil internal friction angle and cohesion under freeze-thaw cycles, this study preliminarily determined the best ratio of water retention and freeze-thaw resistance of three commonly used soil conditioners. To a certain extent, this study can provide theoretical basis and reference for the use of common soil conditioners in alpine arid areas, and provide reference for the use of soil conditioners for ecological restoration of harsh environmental conditions.