The invention relates to a microfluidic device, a preparation method thereof and a microfluidic system. The preparation method comprises the following steps: providing a shaping mold with a groove; liquid metal is injected into the groove, the liquid metal is solidified, and solid metal is obtained; separating the solid metal from the shaping mold, and arranging an electrode on the solid metal; forming a coating layer on the surface of the solid metal with the electrode, and enabling at least part of the electrode to extend out of the coating layer to obtain a prefabricated device; placing theprefabricated device in the substrate solution and curing the substrate solution to obtain a microfluid device; wherein the substrate is formed after the substrate solution is solidified, at least part of the electrode extends out of the substrate, and heat is released in the solidification process of the substrate solution so that the solid metal can be melted. The preparation method is simple,good in encapsulation, high in device integration and easy to industrialize, and the prepared microfluid device is good in formability, excellent in performance and wide in application field and can be integrated with a power supply, a signal transmitter and a signal receiver to form a microfluid system.