Abstract: The Ni(OH)2 was precipitated on the silicon powder surface by chemical precipitation method, and then the in situ synthesized NiO was used to catalyze the nitridation of silicon powder to prepare the Si3N4 powder. The effects of in situ synthesized NiO content (0-2.0wt%) and nitridation temperature on the nitridation of silicon powder were studied. The results show that the in situ synthesized NiO improved the nitridation of silicon powder. With the increase of NiO content, the nitridation rate of silicon powder first increased then decreased. With the increase of nitridation temperature, the nitridation rate of silicon powder increased gradually. The silicon powder with NiO content of 1.0wt% was nitrided completely at the temperature of 1 400 ℃. The prepared Si3N4 showed a whisker-like shape with diameters of 65-497 nm and its growth accorded with the solid-liquid-gas-solid (SLGS) growth mechanism.