Objective: To study the effect of casein hydrolysate (CH) on hypertensive rats. Method: Hydrolysate of casein was desalinated by macroporous adsorption resins DA201C. Angiotensin converting enzyme (ACE) inhibitory activity and antihypertensive activity of casein hydrolysate at the dose of 500, 1 000 mg/kg were measured. Results: CH had significant inhibitory activity against ACE (the inhibitory rate 80.1%), and low concentration (500 mg/kg bw?d) had remarkable antihypertensive activity on spontaneously hypertensive rats (SHR), and extremely remarkable at high concentration (1 000 mg/kg bw?d). Conclusion: Casein hydrolysate showed antihypertensive activity in SHR.