The effect of pulsed high-voltage discharge on mass transfer and reaction processes in a needle-plate reactor was studied. Bubble size distributions and characteristic parameters were determined by photography, implying that inlet air bubbles could be broken into smaller ones effectively by discharge. The mass transfer parameters including specific interfacial area (a), volumetric mass transfer coefficient (k (L) a), and liquid-side mass transfer coefficient (k (L)) were obtained by Danckwerts-plot, reflecting the mass transfer processes. In addition, 4-chlorophenol (4-CP) decomposition was determined under the same experimental conditions. The results showed that the conclusions of 4-CP removal were coincided with the statistical results of bubble images, illustrating that higher peak voltage, pulsed frequency and appropriate air flow rate are beneficial to mass transfer and reaction. However, there was a slight difference between 4-CP removal and mass transfer parameters at higher air flow rate. Therefore, it is more reasonable to optimize the operating conditions of a pulsed high-voltage discharge reactor via combining image acquisition and mass transfer parameters with the results of pollutant degradation.