Abstract: The expansive soil samples reinforced with biaxial geogrid are adopted to carry out a series of tests at different dry density.Effects of reinforcement on the strength and deformation characteristics of expansive soil at different dry density are analyzed.Unconfined compression tests indicate,when higher dry density and the water content less 2% than the optimum quantity,reinforcement has great effects on the stress-strain features,and increment of the peak and residual strength,and the corresponding strain are great after reinforced.Whereas,reinforcement has great effects on the stress-strain features when lower dry density and the water content more 2% than the optimum quantity.The consolidated undrained triaxial tests indicate,the peak strength and hardening degree of expansive soil are improved after reinforced,and effect of dry density on strength and deformation characteristics is also different upon water content.