Abstract: In order to protect the ecological environment and reduce the project cost, the excavated weathered sandstone is crushed and mixed with a certain proportion of loess, bentonite, cement and pumping agent for solidification and improvement as the fluid-filling materials. Based on the backfill project of a foundation pit in Lanzhou, through orthogonal design, the rapid shear tests on the fluid-solidified soil with different proportions are carried out. The influence factors and significance of shear strength are analyzed, and the regression equation for the shear strength is given. The tests show that the most significant factors affecting the internal friction angle and cohesion are the pumping agent and the bentonite respectively. The order of influence of each factor on the internal friction angle can be arranged as follows: pumping agent→ cement→ fine aggregate of weathered sandstone→ loess→ bentonite→ coarse aggregate of weathered sandstone. The order of influence on the cohesion can be arranged as follows: bentonite→ coarse aggregate of weathered sandstone→ pumping agent→ loess→ fine aggregate of weathered sandstone→ cement. According to the test results of various proportions, the regression equation for predicting the internal friction angle and the cohesion of the fluid-solidified soil is established. The research results have certain reference value for evaluating the weathered sandstone as the fluid-filling materials.