The invention relates to a nanocomposite for synchronously removing carbon, nitrogen and phosphorus and a preparation method of the nanocomposite. The method specifically comprises the following steps: flushing natural clinoptilolite with deionized water, and drying the natural clinoptilolite; performing constant-temperature turnover impregnation on the dried natural clinoptilolite by use of a soluble calcium salt solution, so as to obtain the pretreated natural clinoptilolite; adding the pretreated natural clinoptilolite into a mixed solution containing soluble calcium salt, alkali and polyethylene glycol, and stirring the mixed solution till uniform dispersion; slowly and dropwise adding an H2O2 solution into the mixed solution, and performing centrifugation and drying to obtain the nanocomposite. Compared with the prior art, the nanocomposite provided by the invention has fairly strong adsorption capacity and oxidation capacity on pollutants, and efficient and synchronous removal of carbon, nitrogen and phosphorus in different types of actually polluted water can be realized; the removal rate of nitrogen and phosphorus can exceed 80% or more, and the removal rate of carbon is 50% or more; and the nanocomposite has the advantages that the synchronous removal effect of carbon, nitrogen and phosphorus is good, the preparation technology is simple, and the like.