This study intends to adopt a prospective, open, and randomized controlled research method to explore the effectiveness and safety of using human umbilical cord mesenchymal stem cells to treat large-scale burn wounds, in order to break through the limitations of various current treatment methods, explore new clinical treatment methods, promote the repair and healing of skin lesions, and further improve the cure rate and quality of life of patients.

Large area deep burn patients, due to extensive skin defects in their limbs that cannot be repaired by the body itself, need to undergo skin grafting surgery to seal the wound. Although skin transplantation can partially meet the needs of wound sealing, the skin scar hyperplasia after transplantation and healing is significant, affecting the appearance and motor function of the limbs. Moreover, the healed skin lacks dermal tissue and sweat glands and other skin accessories, resulting in poor skin quality after wound healing, And accompanied by obvious discomfort such as fear of heat, itching, and pain, which seriously affects the patient's quality of life. Mesenchymal stem cells have high differentiation potential and can differentiate across embryonic boundaries into epithelial tissue cells such as skin. They can also secrete various cytokines to produce chemotactic and anti apoptotic effects, promoting the formation of wound neovascularization and wound healing. Human umbilical cord mesenchymal stem cells, due to their convenient and painless source, have become good seed cells for promoting wound healing.

Inclusion Criteria:

1. Selected patients are voluntary and sign an "informed consent form";
2. Burn wound area ≥ 20% TBSA, and III ° wound area ≥ 2% TBSA;
3. Age range from 18 to 65 years old, regardless of gender;
4. Plan to perform two or more limb III degree wounds with scab cutting and autologous skin grafting surgery for treatment;
5. No severe heart, lung, blood system, or nervous system diseases;
6. There are no clear complications such as systemic infections.

Exclusion Criteria:

1. Patients who do not agree to participate in this experimental study;
2. Age<18 years old or>65 years old;
3. Patients with definite malignant tumors, AIDS, diabetes, and autoimmune diseases;
4. Pregnant or lactating patients;
5. Individuals with systemic dysfunction;
6. Patients with acute and chronic liver and kidney diseases;
7. Poor compliance makes it difficult to complete the experiment.