The first direct-current triboelectric generator (DC-TEG) based on sliding electrification for harvesting mechanical energy from rotational motion is reported. The DC-TEG consists of two rotating wheels and one belt for connecting them, which are made of distinctly different triboelectric materials with a specific requirement. During the rotation, the contact-induced electrification and the relative sliding between the two wheels and the belt can induce a continuous increase of the accumulated positive and negative triboelectric charges at the two rotating wheels, respectively, resulting in a Corona discharge and producing the observed current through an external load. The DC-TEG can deliver an open-circuit voltage of larger than 3200 V and a maximum power of 100 W under an external load of 60 M at a rotational speed of 1000 r min-1. By designing a point metal discharge electrode near the accumulated positive charges on the metal wheel, the instantaneous short-circuit current can be up to 0.37 mA. The DC-TEG can be utilized as a direct power source to light up 1020 serially connected commercial light-emitting diodes (LEDs) and the produced energy can also be stored in a capacitor for other uses. This work presents a DC-TEG technology to harvest mechanical energy from rotational motion for self-powered electronics.