The invention discloses a polarized light source device based on liquid crystal in a photolithographic lens imaging system. The liquid crystal is used to control the polarization direction of the polarized light in the light path of the photolithographic imaging system, thereby preventing polaroid in the prior photolithographic lens imaging system from being mechanically inserted into the light path, and consequently improving the resolution of the fine variation of the polarization direction. In addition, the polarized light source device can simply and effectively control the direction of the polarized light and facilitate the switchover between the polarized light and non-polarized light which are perpendicular to each other.