In the present study, interactions between two parallel bubbles after the gas jets inject into a liquid cross flow are studied experimentally. For bubble coalescence on the surface of a moving body, the water layer between the twin parallel bubbles possesses initial momentum and bubble coalescence is difficult to conduct. Based on the verification of the repeatability of the experiments, the coalescence mechanism of the twin parallel bubbles subjected to a cross-flow is studied and the effect of re-entrant jet is analyzed, which can reduce the initial momentum of the water layer and promote the coalescence of bubbles. After that, the influences of the initial pressure inside the air chamber and motion speed of the body have been analyzed. The bubble length and its growth rate are proportional to the motion speed of the body and the initial pressure inside the air chamber has little influence on the growth rate of the bubble length. Moreover, only after the stream-wise length of the water layer reaches critical value, bubble coalescence can occur. According to parametric studies, the critical value of stream-wise length of the water layer depends on the motion speed of the body and a correlation has been estimated. •Experiments on bubble coalescence suffering a cross flow were conducted.•Coalescence mechanism of the twin parallel bubbles subjected to a cross-flow was studied.•The influences of the motion speed and the initial pressure inside the air chamber on bubble interactions were studied.•A parameter characterizing bubble coalescence threshold was proposed and a correlation had been estimated.