Microchannels or minichannels are widely used for cooling high density power electronic devices, such as heat pipes and heat exchangers. The interfacial behaviors between liquid and gas phases are very important to understand the flow characteristics in microchannels or minichannels. One of the problems at the capillary pumped loop (CPL) heat pipes is the backflow of vapor through the liquid line toward the evaporator. Therefore, we applied the converging minichannels at the condenser to avoid the backflow. In this paper, a numerical analysis on the interfacial velocities and the total pressures depending on variations of the converging rate and the depth of the minichannels was performed. It was shown that the converging minichannels can reduce the backflow effect. The proper dimension of the minichannels to reduce the vapor backflow was also found.