Contrary to the Adams_Meijer analysis，in this paper it is proved that the public matrix G'in the McElieee's cryptosystem and all other matrices in the R_equiva-lence class of G'are still generator matrices of Goppa codes．This result may be a theoreti-cal support to the Korzhik_Turkin attack while explaining why the Adams—Meijer analy-sis to the McEliece'S cryptosystem conflicts with the real situation．