The present invention relates to an acid salt of amlodipine gentisate and a method of its preparation. More particularly, the present invention relates to a crystalline acid salt of amlodipine gentisate of the following formula 1 prepared by reacting amlodipine and gentisic acid, which is useful for the treatment of cardiovascular diseases and has the advantages of low toxicity, excellent stability, improved pharmaceutical efficacies and long-lasting concentration in blood.