We demonstrate the successful photovoltaic splitting of water microdroplets on a $y$y-cut ${{\rm LiNbO}_3}:{\rm Fe}$LiNbO3:Fe substrate coated with an oil-infused hydrophobic layer. The temporal evolution of the microdroplet contact angle upon a central illumination and the distinct behaviors of two sub-droplets during a following boundary illumination reveal that both electrowetting and electroosmotic effects induced by the dipolar photovoltaic potential on the substrate contribute to the water microdroplet splitting. The reciprocal relationship between the splitting time and the illumination intensity verifies the inherent photovoltaic nature of the water microdroplet splitting. The splitting time is found to be linearly dependent on the initial microdroplet size. These points are quite important to the practicalization of lithium niobate (LN)-based microfluidic chips in the biological field.