The invention belongs to the technical field of lithium ion battery manufacturing, and particularly provides a preparation method of high-capacity lithium ion battery positive electrode slurry. The preparation method comprises the following steps that various raw materials are weighed and subjected to baking processing before use; polyvinylidene fluoride is dissolved into an N-methyl-2-pyrrolidonesolution with the weight 12-19 times of that of polyvinylidene fluoride, and after stirring and filtering are conducted, an adhesive solution A is obtained; a carbon nanotube solution is added into the adhesive solution A, and after the mixed solution is stirred to be uniform, a conducting adhesive solution B is obtained; the conducting adhesive solution B is added into a stirrer in twice, and stirring is conducted to obtain slurry C; ethyl alcohol is added into the slurry C, the slurry viscosity is adjusted with N-methyl-2-pyrrolidone, and after stirring is conducted, slurry D is obtained; and after the slurry D is subjected to processing of a high-speed dispersion machine, filtration processing and vacuum deformation processing, the final slurry is obtained. According to the preparationmethod, in the production process, preparation of the conducting adhesive solution B and preparation of the final slurry are conducted independently and synchronously, and the production efficiency of the positive electrode slurry is effectively improved; and a lithium ion battery prepared from the slurry is low in internal resistance, high in energy density and beneficial to exertion of the maximum gram capacity.