Since the first invention of triboelectric nanogenerator in 2012, it has been developed into a new energy technology. Triboelectric nanogenerator has been applied to efficiently convert the mechanical vibration energy into electricity. The fundamental mechanism of triboelectric nanogenerators is based on the contact electrification and the electrostatic effect. Among these two effects, surface charges transfer happened during the contact electrification process is the main factor to affect the electric output of triboelectric nanogenerators. The electric output of most triboelectric nanogenerators would decrease in environments with high relative humidity, which restricts their application. By using polypeptides as contact materials to construct biocompatible triboelectric nanogenerators, we found that the electric output of the triboelectric nanogenerators can be maintained or is even enhanced at higher relative humidity.