Abstract: The solubility of poplar powder in EmimAC was studied. By single factor and orthogonal experiment, the optimum dissolution conditions were obtained as follows: dissolution temperature 160℃,dissolution time 16 h,moisture content of poplar powder 7.5%, time by ultrasonic waves 10 min. Under the optimum dissolution conditions, the dissolution rate was 48.30%. Furthermore, the total insoluble content of lignin increased at first and then decreased.It reached the maximum value of 29.29% when the dissolution time was 6 h. The structures of poplar powder before and after dissolving were analyzed by SEM,XRD and FT-IR. It was found that structure damage of poplar powder occured when the dissolution time was 16 h, and the crystallinity reduced from 45.43% to 29.03%. However, there are no corresponding derivatives generated from dissolution process. This paper showed that EmimAC was a strong and effective direct solvent.