The invention relates to a thin film circuit and a preparation method of the same. The preparation method of the thin film circuit includes the steps: providing a dielectric substrate; forming a composite metal film layer on the dielectric substrate; forming an electroplating film layer graph by electroplating and thickening the film layer at the uppermost layer of the composite metal film layer in the area where the thin film circuit graph is, wherein the upper surface area of the electroplating film layer graph is greater than the lower surface area of the electroplating film layer graph; and forming a photoresist shielding pattern at the side surface of the electroplating film layer graph, and forming a thin film circuit graph through photoetching. The preparation method of the thin film circuit can avoid etching the side surface of the film layer in the area where the thin film circuit graph is so as to improve the performance of the finally formed thin film circuit.