The invention discloses nickel boride powder with a network structure and a preparation method of the nickel boride powder, and belongs to the technical field of inorganic powder preparation. The nickel boride powder is crystalline Ni3B and has the network structure, and the average diameter of network lines is 20 nm. The preparation method comprises the preparation steps as follows: micron-scale metal nickel powder, amorphous boron powder and alkali chloride powder are mixed; the mixed powder is placed in a corundum crucible, heated to 1000 DEG C or higher under argon protection and cooled naturally after thermal insulation for 0.5-2 hours; an obtained product is soaked in hydrochloric acid, filtered, washed with water and ethanol for several times and dried, and the Ni3B powder with the network structure is obtained. The obtained Ni3B powder is crystalline, has the network porous structure, can be used as a catalyst carrier material and is also a potential inorganic function material.