A method to control the pretilt angle of a liquid crystal device is disclosed. The claimed invention provides two substrates and at least one vertical alignment layers, which are fabricated on one side of each substrate and are opposite to each other. Moreover, a liquid crystal layer is sandwiched between the alignment layers, and the preferred embodiment of the liquid crystal device has an Optically Compensated Birefrigence (OCB) configuration. More particularly, before the process of alignment for the liquid crystal device is performed, a pretilt angle disclosed in the present invention is adjusted since at least one vertical alignment layer is treated with a particle beam generated by plasma or ions. The pretilt angle can range between 5 and 85 degrees.