The unconfined uniaxial compression test of the improved sand under different curing agent contents was carried out in laboratory. The corresponding numerical model was established by using a particle flow numerical simulation software and the numerical simulation test was carried out. In this paper, the microscopic failure mechanism of specimens under different curing agent contents in different loading stages is studied, and it is found that the content of curing agent significantly affects the compressive strength, deformation resistance and macroscopic failure mode of specimens. With the increase of the curing agent content, the peak strength and the elastic modulus increase, while the peak strain decreases. According to the development of the micro cracks, the contact force chain and the particles displacement field evolution process, it can be seen that as the curing agent content increases, specimens are prone to exhibit stress concentration and local failure and gradually develop from the overall failure into local crushing damage. Meanwhile, the bending degree of force chain decreases gradually after fracture and the displacement direction by disorder gradually disperses evenly and orderly, while the failure mode of sample changes from shear failure to tension failure.