Abstract: The microwave source of 8mm wave magnetron(Model ll3A,in China) is studied for the SG-l FELamplifier.FEL requires microwave source to operate insingle source.At present,the magnetron operating8millimeter wave regime is existing in resea ching stage in our country, so it can't be operatedas a single state.A2okW, 34.36GHz magnetron source with a pulse length of 350ns sufioed for request of FEL and hadgood performancesin SG-l FEL experiment. Thispaper shows the microwave source stably operates in single state.