Cu(NO3)2and (NH4)2Mo2O7 were used to fabricate Mo/Cu composite nanopowders by sol-gel technique. The influences of heat treatment process, solution pH value and the addition agent on the particle size were investigated by DTA-TG, XRD and TEM. The results show that under certain heat treatment temperature, the quantity of the addition agent influences the grain size of nanoparticle. When the quantity ratio of addition agent is 0.5, we can get fine nanoparticles with small grain size and homogeneous granularity. The particle sizes are varied under various solution acidities. When pH values change form 1 to 4, the particle sizes increase with the increase of pH value, the most suitable pH value is 1.