The corrosion inhibition behavior of mercaptobenzothiazole (MBT) on copper in 0.1 M H2SO4 solutions was investigated by bulk acoustic wave (BAW) sensor under open-circuit condition in this paper. The growth process of Cu-MBT complex film was monitored by the BAW sensor and the frequency shift curves were acquired. The frequency shift curves were fitted with a proposed model and the maximum frequency shift and the apparent rate constant of film formation were obtained. The relations between them and the concentration of MBT indicated the inhibition ability of the Cu-MBT complex film. The synergistic effects of Br- and I- on the Cu-MBT complex film formation were also compared. It was found that the effect of I- was more obvious than that of Br- at the same concentration of MBT and the growth kinetics of Cu-MBT film changed with the concentration of KI.