1. Striae distensae (SD), also known as stretch marks, are common, permanent dermal lesions that can be symptomatic and are considered aesthetically undesirable; thus, they pose a significant psychosocial and therapeutic challenge. SD arise in areas of dermal stretching and most commonly occur on the abdomen, breasts, buttocks, and thighs. Most literature has described SD during pregnancy(striae gravidarum) and puberty, with reported prevalences varying from 11% to 88%. Hormonal influences, reduced genetic expression of fibronectin, collagen, and elastin, and mechanical stretching of the skin have all been postulated to contribute to SD formation. In the acute phase, SD appear as red/violaceous lesions (striae rubrae; SR) that can be raised and symptomatic. The chronic form (striae albae; SA) exists as hypopigmented dermal depressions.
2. Polylevolactic Acid(PLLA) is at present one of the most promising biodegradable polymers (biopolymers) and has been the subject of abundant literature over the last decade. PLLA can be processed with a large number of techniques and is commercially available (large-scale production) in a wide range of grades.
3. Previous studies have found that 1565-nm laser can promote the synthesis of types I, III, and VII collagen and elastin, as well as the remodeling of dermal collagen. According to previous studies, dermal collagen deposition and remodeling may be related to the mechanism by which 1565-nm laser improves SD.

Inclusion Criteria:

1. Age: 18-50 years old, regardless of gender;
2. The clinical diagnosis was atrophic stria;
3. Patients with normal blood routine, liver and kidney function, and preoperative infection;
4. Able to communicate well with researchers and comply with the overall test requirements;
5. Willing to take and retain photos before and after treatment;
6. Volunteer and sign an informed consent form.

Exclusion Criteria:

1. Scar constitution;
2. Acute or chronic skin infections (including bacteria, viruses, and fungi) exist near the treatment area;
3. Those who are allergic to any component of the product;
4. Those who have been injected with anticoagulant drugs;
5. Those who have used other drugs, other substances, and other implant agents;
6. Patients with severe primary and psychiatric disorders such as heart, brain, liver, kidney, hematopoietic system, endocrine system, etc;
7. History of peripheral vascular disease, long-term alcoholism, diabetes, immunosuppression, disorder, drug abuse, etc;
8. Pregnant and lactating women;
9. Those who are critically ill and difficult to accurately evaluate the effectiveness and safety of the product.