The amount and scale of engineering construction in Xinjiang develop greatly in recent years. Engineering practice necessitates that a comprehensive understanding on the reconstituted loess¢s mechanical behavior to provide theoretical support. In this research，laboratory tests were performed using an infilled loess material from a channel slope in Xinjiang，to investigate the dilatancy and instability of the material which are affected by the degree of compaction. Scanning electron microscope technique and CT technique were used firstly to examine the microscopic and mesoscopic compositions firstly. The stress-strain relationship，the dilatancy and the experienced paths were then analyzed under saturated undrained condition，with consideration of three levels of degree of compaction and three stress levels. Thereafter，the results are compared and verified under drained condition. The findings are below. Firstly，the material could demonstrate contraction-dilation-contraction behavior，between the contractive behavior at loose state and the dilative behavior at dense state. Secondly，the material has a unique critical state line in the stress plane，while its critical states are affected by initial void ratio，suggesting a belt region in the compression plane. Third，the slope of instability line increases with the degree of compaction，indicating a higher stress ratio to achieve instability region. Therefore potential instability led by engineering disturbance reduces at a higher degree of compaction.