Production method of cycloamylose (CA) has been developed using native starch as an economically more beneficial substrate than commercial amylose. However, the yield of CA products from starch is lower than that from commercial amylose. Thus, the objective of this study was to improve the yield of CA products using high amylose corn starch (HACS) that has the highest amylose content (approximately 70%) among native starches. The reaction conditions of isoamylase were optimized to maximize debranching yield of HACS. After debranching, CA was produced by the action of Thermusaquaticus 4-α-glucanotransferase (TAαGTase) for various reaction times. Remaining linear glucans were removed by glucoamylase under the optimum conditions. As a result, the maximum conversion yield of CA from HACS was71% that was 2.2-fold higher than that from rice starch (e.g. Ilpummi; 32%). The degree of polymerization (DP) of CA products ranged from 7 to 41, with DP26 showing the highest yield. This DP profile was very similar as that of CA produced using commercial amylose. Also, a significant amount of larger cyclic glucans were produced from HACS, which was not the case for CA from rice starch. These results were attributed to the unique molecular structure of HACS such as high amylose content and long branch chain length. The high yield production of CA from HACS could be beneficial for industrial applications.