The invention provides a positioning tool and a busbar mounting method. The positioning tool includes a first mount, a second mount, a first link, a second link and a positioning base. The first mount and the second mount are configured to be mounted on opposite sides of the server cabinet, respectively. The first link and the second link are spaced apart from each other. Opposite ends of the first link are respectively pivotally connected to the first mount and the second mount. Opposite ends of the second link are respectively pivotally connected to the first mount and the second mount. The positioning base is pivotally connected to the first link and the second link. The positioning base is located between the first mount and the second mount and is configured to position the busbar.