The invention provides a polyhexose extraction method from the sugar cane bagasse. The method is realized by that after the degreasing processing is performed to the sugar cane bagasse, one or more of cellulolytic enzyme, papayotin and pectolytic enzyme can be hysrolyzed for 0.5 to 1.5 hours under pH value of 4 to 6 at the temperature of 40 to 80 DEG C, treated for 0.5 to 1.5 hours under the supersonic wave with the frequency of 59KHz, and filtered, and finally the polyhexose in the filtrate water is precipitated through ethanol. The method of the invention adjusts the types and the dose of the enzyme on the technology base of eumycete polyhexose extraction, and finds a low energy consumption and efficient sugar cane bagasse polyhexose extraction method under the enzyme processing and supersonic wave extraction technology.