Due to the demand on microfluidic handling, the surface tension in microchannel has attracted lots of attention recently. For controlling surface tension in microchannel, two major ways were reported, thermocapillary (Marangoni effect) and electrocapillary (electrowetting) methods. Here, a new surface tension controlling method by polarization of liquid in the microchannel is proposed, it is called polar capillary effect. The proposed method can change the solid-liquid interface at electrodes from hydrophobic to hydrophilic characteristic. In order to verify the feasibility, several microchannels with electrodes are designed and fabricated. One of sealed microchannels is fabricated and tested successfully. It is found that the liquid (DI water) in the capillary is motionless with input voltage under 2 volts. While the voltage is raised to 3 volt, the liquid flows smoothly in microchannel with the velocity of 69-μm/min. Besides the polar capillary effect, the capillary effect is also tested to identify the key factors within it, that help with the improved design of polar capillary in the future.