The coalescence of nitrogen bubbles in liquid was studied by using a high‐speed motion picture camera at speeds up to 3,000 frames per second. Examination of the films frame by frame reveals that the general process of bubble coalescence is growth‐touching‐coalescence‐vibrating‐detachment. A small amount of surface active additive influences the time of coalescence significantly: 0.9ppm of sodium lauryl sulfate (SLS), 1.6 ppm of sodium laury benzene sulfonate (SLBS) or 1.8 ppm ofn‐octanol inhibits the bubble coalescence completely. This phenomenon is attributed to the dynamic surface effect or the departure from static surface tension caused by extension of the gas‐liquid interface.