Eight kinds of free L-amino acid esters including L-phenylalanine ethyl ester, L-phenylalanine n-butyl ester, L-phenylalanine i-butyl ester, L-tyrosine n-butyl ester, L-tyrosine i-butyl ester, L-tyrosine i-amyl ester, L-aspartic n-butyl diester and L-aspartic i-butyl diester were synthesized by direct esterification of L-amino acid and alcohol with acidic ionic liquid assisted by strong acidic cation resin as catalyst. The structures of free L-amino acid esters were characterized by 1HNMR. Optimal reaction conditions were obtained when synthesizing L-phenylalanine n-butyl ester. Among eleven kinds of the acidic ionic liquids used in this case, [Hmim]HSO4 indicated excellent activity and the catalyst is easily regenerated and reused. By this token, it exhibits its potential application as catalyst and co-solvent in the esterification of amino acid.