Abstract: The extraction conditions of chitin from Periostracum Cicadae,Oxya chinensis(Thunberg),Blaps rynchopetera Fairmaire were optimized by acid—alkali method laying a strong emphasis on the effects of NaOH and HCl on the removal of protein and inorganic salt.The conditions of extractions of chitin from Periostracum Cicadae were:(1)Removing protein: processed the sample with the solution of 6% NaOH,80 ℃,keeping for 1 hour;(2)Removing inorganic salt: put the sample in the solution of 0.2 mol·L-1 HCl,keeping for 20 min at room temperature.Extractions from O.chinensis were(1)Removing protein: 7% NaOH,80 ℃,keeping for 1 hours;(2)Removing inorganic salt: put the sample in the solution of 0.3 mol·L-1 HCl,keeping for 10 min at room temperature.Extractions from B.rynchopetera were(1) 7% NaOH,80 ℃,keeping for 5 h;(2) 0.2 mol·L-1 HCl,keeping for 10 min at room temperature.The structures of chitin extracting from the three insects were the same as standards according to the IR and X-ray diffraction spectra.