Disclosed herein are autocleaved peptide linkers for producing purified proteins. The autocleaved peptide linkers are inserted between a chitin binding protein (CBP) and a target protein to form a fusion protein. Upon expression of the fusion protein, it is allowed to pass a chitin matrix so that the CBP portion of the fusion protein may be bound with the chitin matrix, the peptide linker then undergoes auto-cleavage in a buffer solution at a pH value of about 5.5-7.5 to release the target protein. The chitin matrix may be regenerated with another buffer solution at a pH value of about 3-4, that is, to release the bound CBP and return to its unbound form. The chitin matrix may be reused for at least 6 times without losing its function.