This is a multi-center, prospective, randomized, controlled study. The patients with STEMI who were to undergo PPCI were divided into PCSK9 inhibitor group (n=80) and conventional treatment group (n=80) using the interactive web response system (IWRS), at a 1:1 ratio. In the PCSK9 inhibitor group, a dose of PCSK9 inhibitor (alirocumab) was injected subcutaneously immediately after PPCI and was administered every two weeks thereafter for 3 months; the control group received conventional treatment. Cardiac Magnetic Resonance Imaging (MRI) were used to measure myocardial salvage index at 1 week after operation as primary endpoints. Eject fraction at 6 months after operation will also be measured by MRI as secondary endpoints. Serum TnI/T，CKMB levels were detected q8h for three times and and LDL-C levels were detected at 1 month, 3 months and 6 months after operation. Blood inflammation indicators were detected before and 1 week after the operation, and 6 months after the operation.

Inclusion Criteria:

1. The age is greater than 18 years old and less than or equal to 80 years old.
2. Patients who are clinically diagnosed with STEMI onset within 24 hours and who are planning to undergo PPCI .
3. Signed informed consent.

Exclusion Criteria:

1. Patients who are allergic to PCSK9 inhibitors.
2. Multivessel disease planned for selective intervention within half a year.
3. Patients who have previously undergone revascularization.
4. Pregnant women or women who plan to become pregnant in the next 2 years.
5. Patients whose life expectancy is less than 1 year.
6. Severe liver or kidney dysfunction (ALT>5 times ULA, eGFR<15ml/min/1.73m2)
7. Known active malignant tumor diseases.
8. Patients considered by the investigator to be unsuitable to participate in this study.