The invention discloses a process for preparing hirudin peptide for reducing harmful bleeding reaction of hirudo. The process comprises the following steps: grinding and homogenating dried hirudo, adding 10000NFU/g of pepsin at 36-38 DEG C and pH of 2.0, and performing enzymolysis for 8 hours and above; performing alcohol precipitation on enzymatic hydrolysate, and concentrating and lyophilizing the filtrate to obtain hirudo extract. The hirudo extract PHL prepared by using the method can be used for inhibiting the process of atherosclerosis on the premise of not influencing the blood coagulation factor of endothelial cells. A reliable preparation process is provided to a safe and reliable novel oral preparation which can be clinically used for preventing atherosclerosis for a long time and has weak harmful bleeding reaction.