Abstract: Adsorption properties of Cu2+ in water after modification of corn straw adsorbent were studied.Pretreatment of corn stalk with NaOH and physical treatment with microwave radiation were used.Citric acid containing multi-functional small molecules was selected for esterification reaction with corn stalk.Modified corn stalk adsorbents with strong adsorption properties were prepared by adding carboxyl functional groups.Effect of modified corn straw adsorbent on adsorption under different conditions was studied.Results showed that adsorption effect of Cu2+ was best when adsorbent dosage was 0.8 g，pH value was 5，reaction time was 90 min，reaction temperature was 35 ℃，and initial concentration of solution was 60 mg/L.Modified corn straw adsorbent has good adsorption performance for Cu2+.