Exploiting novel devices for either collecting energy or self-powered sensors is vital for Internet of Things, sensor networks, and big data. Triboelectric nanogenerators (TENGs) have been proved as an effective solution for both energy harvesting and self-powered sensing. The traditional triboelectric nanogenerators are usually based on four modes: contact-separation mode, lateral sliding mode, single-electrode mode, and freestanding triboelectric-layer mode. Since the reciprocating displacement/force is necessary for all working modes, developing efficient elastic TENG is going to be important and urgent. Here, a kind of elastic-beam TENG with arc-stainless steel foil is developed, whose structure is quite simple, and its working states depend on the contact area and separating distance as proved by experiments and theoretical calculations. This structure is different from traditional structures, e.g., direct sliding or contact-separation structures, whose working states mainly depend on contact area or separating distance. This triboelectric nanogenerator shows advanced mechanical and electrical performance, such as high sensitivity, elasticity, and ultrahigh frequency response, which encourage applications as a force sensor, sensitivity scale, acceleration sensor, vibration sensor, and intelligent keyboard.