Apricot almond meal was hydrolyzed simultaneously with Neutrase and N120P proteases. The hydrolysate almond peptide (AP) was fractionated into three ranges of molecular weight (AP-I, >5 kDa; AP-II, 1–5 kDa; AP-III, <1 kDa) using an ultrafiltration membrane bioreactor system. The AP-III brought about a high angiotensin-I-converting enzyme (ACE) inhibitory activity with IC50 value of 0.138 mg mL−1 and the content of hydrophobic amino acid of AP-III was 50.08%. Lineweaver–Burk plots suggested that AP-III acts as a non-competitive inhibitor to inhibit ACE. And we evaluated the stability and in vivo antihypertensive activity of AP-III. Multiple dose oral administration (100 mg kg−1 body weight (BW), 400, 800 mg kg−1 BW) to spontaneously hypertensive rats led to a significant decrease in blood pressure for AP-III. Additionally, the gel filtration and RP-HPLC were used to separate ACE inhibitory peptides from the hydrolysate. The results suggested that the peptide derived from apricot almond protein may have potential applications as functional food.