Ultrasonic attenuation properties of two kinds of pored Al alloy were studied between 1MHz and 10MHz.. The results show that the ultrasonic attenuation properties are determined by the pore structures of Al alloy. Ultrasonic attenuation coefficient α in porous Al alloy increases with decreasing of pore diameter d, decreasing of porosity Ps , and increasing of specific surface area Sv. However the α in cellular Al alloy increases with decreasing pore diameter d, increasing porosity Ps and increasing specific surface area Sv. Ultrasonic attenuation property of cellular Al alloy is better than that of porous Al alloy when they have the similar pore diameter d and porosity Ps. The origin for different attenuation properties is discussed in these materials.