Abstract: The effect of sisal fiber and polymer curing agent on the engineering properties of sandy soil is examined in this paper. Through a series of triaxial shear tests, the shear strength characteristics of sand improved by sisal fiber and polymer curing agent with different content and lengths are studied. The improvement mechanism is studied in terms of peak deviation stress, stress-strain curve characteristics and shear strength parameters. The results show that the peak deviating stress and cohesion of pure polymer curing agent improved sandy soil are obviously increased. Because the curing agent binds sand particles, the relative sliding of particles during deformation is limited, and the internal friction angle is slightly reduced. With the increasing fiber content, the peak deviation stress and stress hardening characteristics of the soil improved by curing agent increase obviously under different confining pressures. The cohesion and internal friction angle of the soil keep a monotonous increasing trend with the increasing fiber content. Given the fiber content of 0.4%, with the increasing fiber length, the shear strength of composite sand improved by fiber and polymer curing agent increases first and then decreases. When the fiber length is 18 mm, the shear strength of soil reaches the maximum and cohesion reaches the maximum of 207.57 kPa. The change in fiber length has little effect on the axial strain and the internal friction angle of soil when the sample is damaged.