At different locations of Boc-L-tyrosine, the selective preparation method of methylation ramifications is studied. Selective methylation reactions of Boc-L-tyrosine and methyl iodide or dimethyl sulphate with the existence of different alkalis are carried out, and N/O-methylation Boc-tyrosine ramifications such as Boc-L-tyrosine methyl ester, Boc-4-methoxyl-L-phenylalanine methyl ester and Boc-N-methyl-4-methoxy-L-phenylalanine are easily prepared.