Using cobalt salt and M salt (M=Zn²⁺,Cu²⁺,Ni²⁺) as raw material and oxalate as precipitant,a series of mixed oxalate precipitates MCo₂(C₂O₄)₃ were prepared as intermediates with a hydrothermal approach.Then these intermediates were pyrolyzed at 400~500 ℃ about 2 hours and finally self-assembled nanoparticles super-structure material of MCo₂O₄ was achieved.A thermo-gravimetric analyzer (TGA),X-ray diffraction (XRD) device and transmission electron microscopy (TEM) were applied to characterize the heat stability,crystallization,morphology and structure of intermediates and target product.The results show that the thermo-gravimetric process of intermediates includes two stages:the loss of crystal water and the thermo-decomposition of oxalate,and the thermal-decomposition temperature should be set more than 370 ℃.The prepared products are superstructure material assembled by fine and homogeneous polyhedral particles,with the particle size of 15~30 nm.The morphology and crystallization of target product are influenced by the intrinsic properties of samples and the types of additives.