The invention discloses a process for preparing sugar from sugarcane. The process comprises the following steps: step 1, subjecting sugarcane to cleaning, chopping, squeezing and filtering successively so as to obtain bagasse and sugarcane juice; step 2, carrying out steam explosion on the bagasse and collecting bagasse having undergone steam explosion; step 3, sprinkling a compound enzyme solution onto the surface of the bagasse having undergone steam explosion so as to obtain enzymatic hydrolysate; step 4, heating the enzymatic hydrolysate, carrying out preliming, introducing nitrogen and carrying out settling separation so as to obtain first clear liquid; step 5, heating the first clear liquid, carrying out preliming, introducing ozone and carrying out settling separation so as to obtain second clear liquid; and step 6, heating the second clear liquid to a boiling state, removing impurities through filtering, carrying out cooling to room temperature and then successively carrying out ultrafiltration, evaporative concentration, crystallization and purging. Sugar prepared in the invention does not contain SO2, so the chromatic value and turbidity value of the prepared sugar are effectively reduced, and the purity and concentration of the prepared sugar are improved.