Abstract: Mechanical energy harvesters have been rapidly developed because of their promising applications in the fields of ocean energy harvesting, human motion mechanical energy, and self-powered energy. In order to collect low-frequency vibrational mechanical energy from the environment, we designed a vibration energy harvester based on CNT/graphene composite aerogel. Since the sheets of graphene aerogel will form double electric layers with electrolyte and the solvated anions in the diffusion layer migrate during the mechanical reciprocating compression process, it will make electrons to move in the external circuit to generate electricity. The results show that the energy harvester can provide a stable output voltage of 215.6 mV with an output power density of 2.12 mW/g at a low frequency of 0.2 Hz, and maintains an output voltage of 161 mV after 10, 000 compressions, realizing the conversion of mechanical energy into electrical energy in the form of electrochemistry. In this paper, the performance influencing factors of the device are analyzed in detail, and the optimal operating conditions are summarized. In addition, the device is also used to collect mechanical energy during human activity, which can produce an output voltage of 240 mV, further demonstrating its application value in the field of human motion energy harvesting.