The invention discloses a method for preparing concentrated sugarcane juice. In the traditional method for preparing the concentrated sugarcane juice, phosphoric acid and lime water are added after sugarcane is squeezed into juice to generate a chemical reaction to generate phosphate, so that impurities are precipitated out from the sugarcane juice. The concentrated sugarcane juice prepared by the traditional method is deep in color, reddish and astringent due to the residual phosphate radical and lime water in the sugarcane juice and enzyme and pigment in the sugarcane. In the method, any additives and other chemical medicaments are not added in the preparation process, so the quality safety of products is guaranteed, the nutrient and the flavor of the sugarcane juice are maintained to the utmost extent, the concentrated sugarcane juice prepared by the method has good color and luster and rich flavor and is fresh, sweet and delicious, and the problem that the concentrated sugarcane juice is off-color and has bad mouthfeel for a long time due to the influence of the pigment, the enzyme, the lime and the phosphoric acid is solved.