The triboelectric nanogenerator (TENG) is a unique revolutionary technology for harvesting energy from the environment and transforming that energy into electricity. The present paper proposes a double rocker triboelectric nanogenerator (DR-TENG), which is used to harvest energy from intermittent reciprocating motions and ultimately obtain electric energy in a controllable manner. The DR-TENG comprises a mechanical transmission structure, generation unit, and shell. The mechanical energy harvested by the pendulum rod is stored in a spiral spring via the mechanical transmission structure, and the energy is then transformed into controllable electric energy through a switching structure and generation unit. The experimental results show that the open-circuit voltage of the DR-TENG is 450 V, the short-circuit current is 36 μA, and the peak power is 11 mW. In a water-wave simulation experiment, the DR-TENG powered 400 LEDs in series and a commercial thermometer with a bridge rectifier. This paper provides an effective method for the harvesting of irregular full-stroke energy in an ultra-low-frequency environment.