NOVELTY - Producing bioactive peptide involves in alkali condition, mixing chitosan and epoxy chloropropane and stirring, adding diamine compound, separating liquid after the reaction, after dissolving the solid with dilute acid, adding sodium tripolyphosphate and ferroferric oxide to obtain modified magnetic chitosan particle; making modified magnetic chitosan solid particle by putting the particle into phosphate buffer with glutaraldehyde; producing peanut protein meal; dissolving peanut protein, adding the solid particle and decomposing, purifying to obtain peanut bioactive peptide dry powder.    USE - For producing bioactive peptide (claimed) used in reducing blood pressure and antioxidation.    ADVANTAGE - The preparation method is low cost, has short production cycle, provides high production yield, provides high purity; is environmental friendly and energy saving; and prepares peptide that has good solubility.    DETAILED DESCRIPTION - Producing bioactive peptide from peanut cookies meal via immobilized enzyme, involves producing magnetic chitosan particle via chemical modification: in alkali condition, mixing chitosan and epoxy chloropropane and stirring for 1-2 hours at 50-100 degrees C, adding diamine compound for 1.5-2.5 hours of further reaction, separating liquid after the reaction, taking solid to spare, rate of charge of that is 3-5 ml of epoxy chloropropane and 1-5 ml of diamine compound per gram of chitosan powder; after dissolving the solid with dilute acid, adding sodium tripolyphosphate and ferroferric oxide with grain size is less than 100 nm and purity is not less than 95%, stirring with ultrasonic, adding sodium tripolyphosphate is 0.05-0.1 times of the weight of the solid, and adding ferroferric oxide is 0.25-0.75 times of the weight of the solid, absorbing the solid particles in the system with magnet to obtain modified magnetic chitosan particle; magnetic chitosan fixing composite proteinase: putting the modified magnetic chitosan particle into the phosphate buffer with glutaraldehyde (2-5 vol.%), stirring at room temperature for 1-3 hours, adding phosphate buffer with compound protein enzyme, stirring 3-6 hours, absorbing the solid particles in the system with magnet to obtain modified magnetic chitosan solid particle, where the concentration of the phosphate buffer 0.05-0.2 mol./L and the pH is 6.8-8, the rate of charge is 10-30 ml of phosphate buffer with glutaraldehyde and 2-6 ml of diamine compound per gram of phosphate buffer with composite protease, and the quantity final concentration of the composite protease at system is 0.1-2.5%; producing peanut protein meal: crushing the peanut cookie, deoiling, extracting peanut protein via alkali extraction and acid precipitation; producing peanut bioactive peptide: dissolving the peanut protein via distilled water, adjusting the pH to 8-10.5, adding modified magnetic chitosan solid particle at 35-50 degrees C and decomposing with enzyme (3000-4000 u/g) for 2-4 hours, adjusting pH of enzymolysis reaction system to 7 after the reaction ends; purification of the peptide: taking the enzymolysis reaction system, getting rid of solid particle, centrifuging the left liquid, taking liquid supernatant, bleaching via activated carbon adsorption, desalting via nanofiltration membrane, detaching via ultrafiltration membrane to obtain peanut bioactive peptide refined liquid, concentrating, spray drying to obtain peanut bioactive peptide dry powder.