Provided is a rhomboid structured triboelectric nanogenerator based on a built-in U-shaped support. The device includes a diamond-shaped bracket and two U-shaped supports. The U-shaped supports is connected with the diamond-shaped bracket through four connecting rods, and the supporting plates of U-shaped supports are sequentially adhered with metal conductor layer and a dielectric material layer, which forms the power generation unit. When the diamond-shaped bracket is closed, the dielectric material layers on the two supporting plates come into contact to produce friction charge; and then subjected to the reverse force after compression of the spring, the two dielectric material layers are separated, so as to generate an induction electric field by the friction charge and form a potential difference. Compared with an existing vibration energy harvester, the advantages will be small space occupation, a long service life, simple fabrication, and a high energy conversion rate.