The invention belongs to the technical field of synthesis of inorganic nano materials and discloses a preparation method of a porous cobaltosic 
oxide nanobelt. The preparation method of the porous cobaltosic 
oxide nanobelt comprises the following steps: (1) firstly dissolving 
cobalt salt and a precipitator into water, so that a 
mixed solution is formed; (2) placing the 
mixed solution into a hydrothermal kettle, carrying out a 
hydrothermal reaction for 5-24 hours at the temperature of 100-250 DEG C; (3) after the 
hydrothermal reaction is finished, separating and washing reaction products, and then 
roasting the reaction products at the temperature of 350-800 DEG C, so that the porous cobaltosic 
oxide nanobelt is obtained. According to the preparation method of the porous cobaltosic oxide nanobelt, no surfactant or 
organic solvent is adopted in a synthetic process, and a new synthetic method is provided for a multilevel structure 
copper oxide material; a preparation technology is simple, the whole technological process is carried out in a reaction kettle, no complex equipment is needed, and the preparation method of the porous cobaltosic oxide nanobelt is simple, efficient, low in cost, 
environmentally friendly and easy for large-scale synthesis.