The present disclosure provides a thin film transistor liquid crystal display panel and a preparation method thereof. The display panel has an array substrate, an opposite substrate and a frame sealant, and has a substrate layer, a first protective passivation layer, an organic film layer, and a second protective passivation layer, wherein an orthographic projection of the second protective passivation layer on the substrate extends to an outer region outside the frame sealant. The display panel further has a water insulation layer, which covers a portion of the second protective passivation layer where its orthographic projection on the substrate layer is in the outer region, such that the second protective passivation layer is not in contact with an external environment of the display panel. The thin film transistor liquid crystal display panel provided in the present disclosure may prevent the exhaust gas of the organic film from influencing the TFT performances, while ensuring the water resistance of the display panel under harsh conditions.