Under microwave irradiation, caprolactam and tetrabutyl ammonium chloride as raw material, synthesized a new coordinated ionic liquid-(C4H9)4NBr•C6H11NO. The effects of reaction time and microwave power to the results were studied. The structure of the compound was characterized via IR. To find the thermal stability range the compound was detected using TGA-DTA. The results indicated that when microwave power is 210W and reaction time is 90s the coordinated ionic liquid had the best properties. The pH value and the conductivity of the compound was 8.9 and 573λs•cm-1 respectively at 20℃. Compared the spectra of IR of raw materials and product, we found there were new absorption peaks in the product, which showed that the product was not a simple mixture but a new coordination compound. Via TGA-DTA pattern, we obtained that this coordinated ionic liquid can be a stable existence from room temperature to about 250℃.