Abstract: Feasibility of preparing activated carbon from bamboo knot with phosphorous acid by microwave radiation was studied.Effects of microwave power,activation time and phosphorous acid solution concentration on the quality of activated carbon was investigated.Optimum technology and result were obtained as follows:microwave power 560 W,activation time 9 min and phosphorous acid solution concentration 40%(wt %),iodine value of activated carbon (889.0 mg/g),decolorizing capacity for methylene blue 178 mL/g and yield 31.0%.The activation time of this process was 1/45 times as fast as the conventional process.The decolorizing capacity for methylene blue was 1.48 times as much as that specied in National Standard(GB/T 12496.10-1999).A new way on utilizing bamboo knot resource was provided by this method.