Abstract: The resistance of graded broken stone to vibratile compacter was used to study the change of compaction state by analyzing the interaction between vibrating compacter and graded broken stone with dynamics.Utilizing state identification theory and automatic testing technology,the resistance reflecting the change of compaction state during compacting process was obtained by continuous testing the interaction.the quality of compaction could be judged and the relation between resistance and density of material could be obtained by the change of resistance of graded broken stone.Through the tradition that density must be used to appraise the compaction state of material was abandoned,and the basis for continuous monitoring the compaction quality of graded broken stone subgrade in-site was established.