The invention provides a system for treating a chloroaluminate ionic liquid spent catalyst and alkaline wastewater. The system comprises a hydrolysis reactor, a neutralization reactor, a flocculationsedimentation system, a mechanical dehydration device and a drying device, wherein the hydrolysis reactor is used for mixing the chloroaluminate ionic liquid spent catalyst with strong brine for hydrolysis reaction; the neutralization reactor is connected to the hydrolysis reactor and is used for mixing acidic hydrolysate generated by hydrolysis reaction with alkali liquor containing the alkalinewastewater for neutralization reaction; the flocculation sedimentation system is connected to the neutralization reactor and is used for fully mixing neutralization liquid generated by neutralizationreaction with a flocculant and carrying out sedimentation separation; the mechanical dehydration device is connected to the flocculation sedimentation system and is used for dehydration treatment of concentrated flocs formed by sedimentation separation; and the drying device is connected to the mechanical dehydration device and is used for drying wet solid residues formed by dehydration treatment.The system can softly eliminate the activity of the spent catalyst, and has good stability and safety of operation.