Linear amylose is degraded to maltose by β-amylase.And the maltose can be determined using the DNS method to calculate the yield of the cyclodextrin.The impacts of substrate concentration,the dosage of enzyme,temperature,pH,maltose,ethanol and dimethyl sulfoxide on conversion rate were studied.The results showed that the conversion rate was the highest when the final concentration of amylose was 0.10%~0.125%.The dosage of enzyme had little effect on the final conversion rate.The optimum pH and temperature for cyclization were 6.5 and 40 ℃.And maltose inhibited the conversion rate.Ethanol and dimethyl sulfoxide improved conversion rates.