Abstract: In response to the problems of harsh reaction conditions and easy solubility of catalysts in the reaction system in the traditional preparation method of oxazolidinone, we proposed the reaction of 2-bromopropene with 1,8-diazabicyclo 5.4.0 undec-7-ene （DBU） to prepare （AIDBU） Br, which was then subjected to anion exchange and imidazole modification to obtain vinyl functionalized ionic liquid （AIDBU） Im, and polymerized with divinylbenzene （DVB） to obtain heterogeneous catalyst P-AD-1/1. In order to confirm the successful synthesize of the P-AD-1/1, a series of characterizations were conducted, such as NMR, FT-IR, XRD and TGA etc. The P-AD-1/1 was then applied to the CO₂-aniline-ethylene oxide cyclization reaction for the preparation of 3-phenyl-2-oxazolidinone, where the effect of the （AIDBU）Im-to-DVB ratio on catalytic activity and catalyst recyclability experiment were investigated. The results indicated that, under the optimal conditions: 20 wt% catalyst, 110 ℃, 2.5 MPa, and 1 h reaction time, achieving 66.3% yield of 3-phenyl-2-oxazolidinone, the P-AD-1/1 showed good recyclability, and the yield of product could still reach 62.3% after five cycles. Furthermore, the reaction pathway of the synthesis of 3-phenyl-2-oxazolidinone from CO₂-phenyl-epoxyethane was studied. This study provides experimental basis and theoretical reference for the application of ionic polymers in the preparation of 3-phenyl-2-oxazolidinone from CO₂-phenyl-epoxyethane.