Abstract: Chitosan cross-linked with 2,5-bis(formic acid)-3,4-diolthiophene(DTCC) was prepared with ethyl chloroacetate,sodium sulfide,diethyl oxalate and chitosan(CTS) as raw materials.The antibacterial effect of cross-linked polymer was studied against a series of test bacterial cultures by quantitative suspension method. Relation between storage time and variation of white peach mass-loss ratio,decomposition ratio,chlorophyll content,film penetration ratio and total saccharine content was examined thoroughly after freshkeeping process with synthesized cross-linked polymer as over-coat film.Results obtained from experiments indicated that partially cross-linked DTCC had a relatively strong antibacterial effect against Gram-positive and Gram-negative bacteria.The mean anti-bacterial ratios of DTCC for pseudomonas aeruginosa(MSH),pseudomonas fluorescens(ATCC13525),bacillus cereus(CIP6624),bacillus subtilis(ATCC6633) are 96.7%,95.8%,97.9% and 98.2%,respectively,after 20 min treatment.The minimal inhibited concentrations(MIC) for 4 bacteia are 25.0,25.0,3.1 and 3.1 g/L,respectively. DTCC also demonstrates strong antibacterial effect on aspergillus niger and penicillium italium:mean antibacterial ratios for above bacteria are 99.0% and 28.4%,respectively,with corresponding MIC of 25.0 and 12.5 g/L after 20 min treatment.DTCC with concentration of 1.0 g/L coated on the outer skin of white peaches shows a good preservation effect after 12 d storage under(27 ± 0.5)℃. The mass-loss,decomposition and film penetration ratios are 8.1%,40% and 34.1%,respectively. The total saccharine content is around 75.1 mg/g.