Abstract: Alkali residue was dissolved by the ammonium hydrogen fluoride method, in which the uranium content is determined to be (16.7±0.3)%(n=6) by inductively coupled plasma optical emission spectrometry(ICP-AES). By means of XRD and SEM-EDS, the main uranium occurrence form of alkali residue was determined. It includes UO₃, fluoride(CaF₂, NaF, MgF₂, UF₄, etc), SiO₂-P₂O₅-UO₃, Cr₂O₃-Fe₂O₃ and other solid melts, and the forms of UO₃ being wrapped by the above solid melts. Using TBP-HNO₃ as complexing agent, the effects of various parameters were investigated on the lab-scale supercritical CO₂ fluid extraction facility. The extraction parameters are optimized: the particle size is 0.250-0.420 mm, saturated Al(NO₃)₃ solution of w=25% alkali residue is used as salting agent, the mole ratio of TBP-HNO₃/U is ≥50, the extraction temperature is 50 ℃ and the pressure is 20 MPa. Under these conditions, the extraction rate of uranium in the alkali residue reaches as high as 98.5% within 2 h. This work provides a new method for the recovery of uranium in alkali residue.