To identify the liquid circulation flow structure in a bubble column, a set of multipoint tracer injection and detection device was developed for a systematic study in a bubble column of 550 cm in height and SO cm in diameter. Tracer response profiles were measured to track the liquid flowing trajectory under various flow conditions in the column with and without draft tubes. They showed that only when the draft tube length was greater than 3 m could the tracer response exhibit obvious periodicity. To resolve the liquid circulation flow structure in the time and frequency domain, wavelet rnultiresolution analysis was adopted. The results showed that the liquid circulation frequency increased with superficial gas velocity, which is in agreement with the published literature. It was also found that the macroscale, mesoscale, and microscale circulation loops coexisted in the bubble column.