The invention provides preparation methods of a gallium nitride diode and a gallium nitride triode. According to the preparation methods of the gallium nitride diode and the gallium nitride triode, a passivation layer corresponding to the position of an unqualified island is reserved in an etching process of the passivation process; a passivation layer window above a qualified island is opened while a passivation layer window above the unqualified island is maintained to be closed; next, the etched passivation layer is covered with a third metal layer; finally, a first metal layer and a second metal layer on the qualified island are connected while the first metal layer and the third metal layer on the unqualified island are insulated, so that the unqualified island can be removed; and meanwhile, a step of re-sealing and insulating after all passivation layer windows are opened is avoided, so that the process is simplified and the cost is lowered.