The invention discloses a molecular marker of an REPS1 gene for early diagnosing osteoarthritis and an expression product thereof.It proves that the REPS1 gene is differentially expressed between synovial tissue of a patient suffering from osteoarthritis and synovial tissue of a normal person by means of a gene chip and a Western blot method, which can be used as an index for early diagnosing osteoarthritis.In addition, the invention further discloses the REPS1 gene and an expression product thereof, wherein the expression product can be used as a target for treating osteoarthritis and used for new drug guidance research and development.