NOVELTY - Method for producing erythritol by utilization of waste erythritol bacterial sludge, involves inoculating a strain subjected to conventional slant activation into a culture medium, culturing, preparing a mixture of an erythritol solution and bacterial sludge, introducing culture solution, processing, separating, collecting the bacterial sludge, subjecting the bacterial sludge to immobilization, adding the immobilization particles into a sterilized fermenting liquid, fermenting, decoloring, purifying, concentrating, crystallizing and separating product.    USE - The method is useful for producing erythritol by utilization of waste erythritol bacterial sludge (claimed).    ADVANTAGE - The method is performed rapidly and simply using cost-effective and easily available raw materials, exhibits high conversion rate, and is suitable for industrial production.    DETAILED DESCRIPTION - Method for producing erythritol by utilization of waste erythritol bacterial sludge, involves inoculating a strain subjected to conventional slant activation into a culture medium (pH 4.5-7.5) containing cane sugar and/or glucose and yeast powder as raw materials, culturing at 25-30 degrees C under condition of oscillation at 100-225 revolutions/minute (rpm) for 24-36 hours to obtain primary seed culture, inoculating primary seed culture in a culture medium (pH 4.5-7.5), culturing at 25-30 degrees C under condition of oscillation at 100-225 rpm for 12-18 hours to obtain secondary seed culture, inoculating secondary seed culture in a fermentation culture medium(pH 4.5-7.5), culturing at 25-30 degrees C under condition of oscillation at 100-400 rpm and dissolved oxygen content of 10-80% for 120-168 hours to obtain culture solution, preparing a mixture of an erythritol solution and bacterial sludge, placing in a fermenting tank, introducing culture solution, processing, separating, collecting the bacterial sludge, subjecting the bacterial sludge to immobilization by utilizing an immobilization carrier to prepare immobilization particles, adding the immobilization particles into a sterilized fermenting liquid comprising glucose and nitrogen source (reduced quantity), fermenting to obtain an erythritol solution, subjecting the erythritol solution to decoloration and ion exchange purification, and concentrating, crystallizing and performing centrifugal separation to obtain erythritol crystals.