Low-level laser therapy (LLLT) as an effective therapy with biochemical change has gained more and more attention in clinical treatment. This review sorts many fundamental experiment studis and clinical applications about LLLT published in recent years, and summarizes the advances of evidence-based proofs of the potential mechanisms of LLLT with different wavelengths in treating osteoarthritis. It shows that LLLT could relieve pain, modulate inflammatory response, protect cartilage, and prevent cartilage degeneration, through increasing cell proliferation, stimulating fibroblasts to produce collagen, bone repair, and regulating inflammatory markers and so on. LLLT with different wavelengths has different effect, and it is important for clinical practice.