Aim To estimate the clinical efficacy of platelet-rich plasma (PRP) injection in the therapy of Chronic Ankle Instabiliy (CAI) in young adults. Methods 80 sufferers with CAI with cartilage injury (from March 2018 to March 2021) enrolled to our hospital were differentiated into two groups at random (n = 40/group). The arthroscopic group and the PRP with arthroscopic group were handled with ankle arthroscopy and PRP injection combined with ankle arthroscopy respectively. The ankle dorsal extension, metatarsal flexion range of motion and pain, ankle function and balance ability were contrasted among the two groups before and 6 months after therapy. The levels of serum indexes were contrasted among the two groups pre-therapy and post-therapy. Results 6 months after therapy, the ankle dorsal extension, metatarsal flexion activity, visual analog score (VAS), American orthopedic foot, ankle society (AOFAS) and Berg Balance Scale (BBS) scores were boosted in two groups, and versus the arthroscopic group, the ankle dorsal extension, metatarsal flexion motion and AOFAS, BBS scores were enhanced and VAS scores were lessened in the PRP with arthroscopic group. The contents of MMP-3, TIMP-1 and TNF- α were boosted in both groups, and versus the arthroscopic group, the contents of MMP-3, TIMP-1 and TNF-α were memorably lessened in the PRP with arthroscopic group. Conclusion The application of PRP injection combined with ankle arthroscopic surgery in the therapy of young CAI sufferers merged with cartilage injury is helpful to relieve ankle pain and improve ankle function.