Based on Danckwerts theory of reaction and mass transfer, using a gas-liquid flow, the interfacial surface per volume in cyclone reactor was determined by chemical absorption. According to the experimental results, the interface area was increased with the cascade density and the kinetic energy factor, furthermore, the relationship of interfacial surface per volume against kinetic energy factor and cascade desity was obtained. As a new type of absorber, cyclone reactor has simple structure and convenient installation. The interfacial surface per volume is higher than that of helical rotating absorber and whirlpool tower plates.