Abstract: A series of N,N'-bis(2-hydroxy benzyl) substituted imidazolidine derivatives(3a～3h) were designd and synthesized by means of combining segments o-hydroxy phenyl and imidazolidine compounds,according to the reinforcement of biological activities.The N,N'-bis-o-hydroxy benzyl diaminoethane(2) was synthesized using salicylaldehyde and 1,2-diaminoethane,through condensation reaction and then reduction by NaBH₄,and further cyclization with aromatic aldehydes.The structures of all the compounds were confirmed by ¹H NMR,IR,mass spectra and elemental analysis.The results show that the reaction of salicylaldehyde with 1,2-diaminoethane only formed the symmetric Schiff base(1),the condensation of aromatic aldehyde with compound 2 was noticeably different for different substituents: o-,p-substituted electron-withdrawing groups can activate aromatic aldehyde and result in a higher yield of ring closing reaction,but o-,p-substitute electron-donating groups have opposite effects.The result of preliminary bioassay shows that the target compounds had obvious specificity to different bacteria at 0.1%(mass concentration),and had an inhibitory rate of 100% on Monilia albican and Escherichia coli.