A visual study was performed on the boiling behavior for binary mixture R141b-R113 by using a high-speed digital camera to record the bubble behaviors during boiling process. The bubble departure diameter, departure time, and nucleation density for boiling heater surface as functions of composition at different heat fluxes for binary mixtures were presented. Strong effects of composition on these three parameters were observed. From the video images, it can be concluded that evaporation of microlayer is very important to the growth of bubble. It is also observed that during the bubble growth process they are not recruited into the microlayer below the bubble.