Abstract: Phycobiliprotein was extracted from spirulina by repeated freeze-thaw and ultrasonic de-freezing,and separated by isoelectric point. The type of protein isolated was determined by SDS-PAGE electrophoresis. The phycobiliprotein was hydrolyzed successively by pepsin and trypsin. The process of preparing angiotensin-converting enzyme(ACE)inhibitory peptide by pepsin and trypsin hydrolysis of phycobiliprotein was optimized by single factor experiment and orthogonal experiment. The results showed that the optimal enzymatic hydrolysis conditions of pepsin hydrolyzed phycobiliprotein were hydrolysis temperature 37 ° C,the substrate mass concentration 6%(w/v),and the enzyme to substrate ratio 5220 U/g.Under the conditions,the ACE inhibition rate was 82.07%. The optimal enzymatic hydrolysis conditions for trypsin hydrolysis of phycobiliprotein were temperature 42 ℃,substrate mass concentration 6%(w/v),enzyme to substrate ratio 5220 U/g. Under the conditions,ACE inhibition rate of 80.35%. The ACE inhibition rate of phycobiliprotein with a molecular weight of less than 3 kDa was 94.30% using an ultrafiltration centrifuge tube.