Abstract: With the rapid development of social economy, Chinese infrastructure is more and more perfect, highway construction has made remarkable achievements. Subgrade is an important part of highway structure, and its bearing capacity directly determines the comfort and safety of driving. Therefore, it is of great significance to do a good job in highway subgrade detection. Sand filling method is the main method to measure the degree of compaction in engineering fi eld, which has the characteristics of simple and rapid operation, and its application in the detection of subgrade compactness has signifi cant eff ect. Based on a comprehensive grasp of the basic principle of sand fi lling method, this paper expounds the application process of sand fi lling method in subgrade detection, and fi nally analyzes and discusses specifi c cases, so as to improve the level of subgrade detection.