Abstract: For simulating the actual working conditions, a series of gradient ratio tests of geotextile filtering clay are completed by using an improved gradient ratio permeameter that can apply vertical load. The tests are carried out under the condition of the critical hydraulic gradient (1.0) and hydraulic gradient equal to 2.0, respectively, with the 4th layer of clay soil in Shanghai and the short fiber needle punched non-woven geotextile. The variation of the filtration performance of geotextile with hydraulic gradient and normal stress is studied by changing the vertical load. The results show that the hydraulic gradient and normal stress are the important factors affecting the clogging characteristics and the permeability of geotextile filter. The gradient ratio of the geotextile filter clay increases with the increase of the vertical load, but there is no impermissible clogging when it is stable. Under a certain load, the coefficient of permeability decreases with time and then tend to stabilize. The stabilized coefficient of permeability decreases with the increase of the vertical load. The hydraulic gradient from 1.0 to 2.0 also causes the increase of the gradient ratio and the decrease of the permeability. The test results better reflect the filtration effect of the geotextile filter under the actual working conditions, which can provide references for similar engineering design.