A series of Schiff bases such as 2-(substituted phenylimino) quinoxaline-3-one were synthesized by nucleophilic addition reaction of quinoxaline-2,3-dione with p-Phenylene diamine followed by the Schiff reaction using different aldehydes in alcholol. A total of five compounds were synthesized by both conventional and microwave oven method with good percentage yield. They were purified and characterized as the basis of their spectral data. The synthesized compounds were screened for in-vivo analgesic activity at a dose of 20 mg/kg body weight. All the compounds showed significant analgesic activity comparable with control and standard drug aspirin in rats described in eddy's hot plate method. Among them, compounds 3e and 3d exhibited potent analgesic activity. Effect of substitution at arylidene part on analgesic activity was studied. Compounds 3e and 3d with electron withdrawing groups were found to be highly potent among the series.