The polymerization inhibitor can be added into unsaturated compound or the system containing unsaturated compound to prevent it from polymerization in process of reaction, separation, utilization and storage, ion liquid can be used as both dissolvant and polymerzation inhibitor. This invention product-novel ion liquid polymerization inhibitor has advantages of: it can be reused, less loss, no deterioration, low total cost, broad utilization fields; and it can be used for unsaturated acids, unsaturated aldehyde, in reaction process, separation, use storage, it is used polymerization inhibitor at the same time being of solvent.