Disclosed is an antihypertensive composition containing as an active ingredient a gelatin extract made from the skins of a skate ray and a peptide isolated from the extract. The present invention is directed to a pharmaceutical composition for a hypertension prevention and therapy containing as an active ingredient a hydrolysate of a gelatin extract isolated from the skins of a skate ray, a method for preparing a hydrolysate of a gelatin extract made from the skins of a skate ray, and the use of a new peptide having an antihypertensive activity isolated and purified from the hydrolysate.