The invention discloses a metal powder electromagnetic wave absorbent and a preparation method thereof. The method takes market carbonyl iron and reduced Ni and Mo powder as raw materials, adopts mechanical alloying technology to prepare the metal powder electromagnetic wave absorbent, has simple technology and convenient operation and can adjust the granularity and the shape of powder by changing ball milling time. The prepared electromagnetic wave absorbent simultaneously contains two types of phases of Fe and FeNiMo with high magnetic conductivity and magnetic loss, has higher magnetic conductivity and magnetic loss and can adjust the magnetic conductivity and the magnetic loss by changing the content of Fe, Ni and Mo.