In response to the development idea of construction saving, rice husk ash is filled into red clay. The effect of rice husk ash on the road performance and micro mechanism of red clay is studied through a series of experiments. The results showed that the liquid plastic limit of red clay changed little with the addition of rice husk ash, the maximum dry density decreased with the increase of rice husk ash, and the optimal moisture content increased. The compressive strength of red clay mixed with rice husk ash increased first and then decreased with the increase of the content, and reached the maximum when the content was 15% and the curing time was 28 days. SEM test showed that the structural compactness of solidified red clay was improved, and in this process cementitious materials were produced. Using rice husk ash to improve red clay could be cost-effective in respect to roadbed stability, and can be beneficial in protecting the environment and realizing sustainable use of resources.