• When signing the informed consent form, the age should be ≥ 18 years old, regardless of gender;

• Clinically diagnosed as a patient with Critical limb ischemia, with a Rutherford score of 4-6.

• Patients who are unable to undergo interventional surgical treatment, or whose previous interventional surgical treatment is ineffective, or who are unwilling to undergo any intervention or surgical treatment, and can only receive conventional antiplatelet and vasodilator drugs (before baseline, antiplatelet and vasodilator drugs must be used for at least 1 week);

• During the screening period, lower limb artery color ultrasound or lower limb computed tomography angiography (CTA) showed severe stenosis or occlusion of one or more of the common iliac artery, external iliac artery, common femoral artery, superficial femoral artery, popliteal artery, anterior tibial artery, posterior tibial artery, and fibular artery;

• During the screening period, if there are severe symptoms of lower limb ischemia, meeting any of the following symptoms is sufficient: There is limb rest pain caused by lower limb ischemia, with a disease duration of ≥ 2 weeks, and a VAS score of ≥ 40mm and \< 100mm before the first administration; There are limb tissue ulcers caused by lower limb ischemia, with a disease duration of ≥ 2 weeks and limb ulcers (4cm2 ≤ maximum single ulcer area ≤ 25cm2);

• All subjects with fertility or their spouses must take effective contraceptive measures within 3 months after signing the informed consent form until the completion of the trial;

• The subjects voluntarily give informed consent and sign an informed consent form (if the subjects and/or their guardians lack reading ability and cannot understand the content of the informed consent, they need to sign together with a fair witness), fully understand the methods and procedures of the experiment, and be able to provide biological samples for testing related indicators in accordance with the experiment requirements.