The invention provides a preparing method for a carbon nano tube foam material. The method comprises the steps that cheap polymer foam serves as a template, the processes of in-situ formation of a catalyst, partial thermal cracking removing of the polymer template, growth of carbon nanomaterials and the like are synchronously carried out by controlling experiment conditions, and the carbon nano tube foam material efficiently grows, wherein the carbon nano tubes are wound and woven into a mesh structure in the three-dimensional directions of a carbon framework and have distributed pore diameters of multiple dimensions, and the obtained material has the large specific surface area, the controllable porosity, good hydrophobicity, excellent electrical conductivity, a unique hollow frame structure, and application value in the fields of composite materials, sensing, oil and water separation and the like. According to the method, reaction conditions such as gas flow, gas introducing time, the reaction temperature and the catalyst are optimized, and thus the carbon nano tube foam material of a foam structure is obtained and has excellent adsorption performance on various kinds of oil and organic solvent. The defect of an existing carbon nano tube foam material preparing method is overcome.