Abstract: Five quaternary salts of hydroximinomethyl-pyrimidines and their derivatives (Ⅲ_a～Ⅲ_c) were synthesized, and their reactivation activities for phosphorylated acetylcholinesterase were studied. These compounds were prepared by quaternization of corresponding hydroximinomethyl-pyrimidines obtained from nitrosation of methyl-pyrimidines with isoamyl nitrite in absolute alcohol in the presence of hydrogen chloride, or by nitrosation of quaternary salts of methylpyrimidines under similar Conditions.Preliminary pharmacological examination showed that these compounds, except Ⅲ_c have no effect in the protection against Paraoxon (E600) intoxication in mice.However, for the reactivation of Paraoxon inhibited acetylcholinesterase Ⅲ_a～Ⅲ_c, are as effective as 2-PAM in vitro.