The invention discloses a method for preparing carbon fiber with a boron nitride coating on the surface from polyacrylonitrile, and belongs to the field of high-temperature anti-oxidization coating preparation. The method for preparing the carbon fiber with the boron nitride coating on the surface from the polyacrylonitrile comprises the following steps of 1, performing oil removal, decontamination and drying on polyacrylonitrile raw yarns; 2, by using absolute ethyl alcohol as a solvent, preparing a boric acid urea soaking solution from boric acid and urea; 3, putting the polyacrylonitrile obtained in step 1 into the boric acid urea soaking solution obtained in step 2 to be soaked; then, performing drying; 4, putting the polyacrylonitrile obtained in step 3 into a pre-oxidization furnaceto be subjected to pre-oxidization; 5, putting the polyacrylonitrile obtained in step 4 into a high-temperature tubular furnace; raising the temperature in a protection gas atmosphere; performing heatinsulation; lowering the temperature to room temperature; then, taking out a sample. The method provided by the invention can solve the problems that other carbon fiber surface boron nitride coatingpreparation methods need high temperature, the process is complicated, the cost is low and the like. The high-temperature anti-oxidization performance of the carbon fiber is improved; the use temperature is raised.