Weeping is an adverse phenomenon which results in higher pressure drop and poorer aeration performance. Visual experiments have been conducted to study the mechanism by which weeping impairs the work perfor-mance of multi-orifice plate. A theoretical model is improved to analyze the weeping phenomenon of multi-orifice plate based on potential flow theory. The relations of different bubbling conditions and weeping rate are analyzed. Weeping condition and average weeping rate have relation with the driven pressure differential and dynamic variation of gas chamber pressure. In addition, a set of experiments are designed to study the influ-ence of various factors on weeping rate. The bubble coalescence during bubble formation is a fatal factor deter-mining weeping rate, so the relation between weeping rate and gas flow rate is conced with the pitch of orifices and orifice diameter. There is a critical plate thickness which is in favor of weeping.