Abstract: In order to study the effect of polyacrylamide (PAM) on the early strength and failure form of lime stabilized soil, through the California bearing ratio (CBR) test, triaxial unconsolidated undrained shear test and super depth of field three-dimensional microscope, the early strength of PAM-lime stabilized soil with different PAM contents was analyzed. The solidification mechanism of PAM on the lime stabilized soil was explored. The research indicates that PAM can effectively improve the early strength of the lime stabilized soil. With the increase of PAM content, the early strength of the lime stabilized soil shows a trend of increasing first and then decreasing. PAM can improve the brittle failure characteristics of lime stable soil, and weak strain hardening occurs. But when the PAM content exceeds 0.36wt%, the lime stable soil exhibits brittle failure characteristics under low confining pressure of 50 kPa. When the content of lime is 8wt% and the content of PAM is 0.36wt%, the improvement effect of the soil is better. Under the condition of this dosage, the combined action of PAM and lime can better promote the agglomeration of soil particles, strengthen the soil structure and increase the surface roughness of the soil. The internal friction angle and cohesion can be improved and the shear strength will also be enhanced.