The invention provides a display panel and a preparation method thereof. Oxide layers are arranged at the joints of a source-drain metal layer and a first gate layer and a second gate layer, specifically, a first oxide layer is arranged at a position, corresponding to a first through hole, of the first gate layer, and a second oxide layer is arranged at a position, corresponding to a second through hole, of the second gate layer. Or, oxide layers can be arranged on the whole surfaces of the first gate layer and the second gate layer. The first oxide layer and the second oxide layer are used for protecting the joint of the source-drain metal layer and the first gate layer or the second gate layer from being corroded by HF, so that the contact resistance of the source-drain metal layer and the first gate layer or the second gate layer is not affected, and the display effect of the display panel is kept stable.