Triboelectric nanogenerators (TENGs) hold great application prospects and research values in the field of energy harvest. The friction layer of TENGs plays an important impact role in their output performance. Therefore, composition modulation of the friction layer is of great significance. In this paper, the xMWCNT/CS composite films with multiwalled carbon nanotubes (MWCNTs) as a filler and chitosan (CS) as a matrix were prepared and a TENG based on the xMWCNT/CS composite films (xMWCNT/CS-TENG) was constructed. The introduction of the conductive filler MWCNT significantly improves the dielectric constant of the films due to the Maxwell–Wagner relaxation. As a result, the output performance of the xMWCNT/CS-TENG is greatly enhanced. The best values of an open-circuit voltage of 85.8 V, a short-circuit current of 8.7 μA, and a transfer charge of 29 nC were obtained in the TENG with an optimum MWCNT content of x = 0.8 wt % under an external force of 50 N and a frequency of 2 Hz. The TENG can sensitively perceive human activities such as walking. Our results evidence that the xMWCNT/CS-TENG is a flexible, wearable, and eco-friendly energy collector, holding great prospects in health care and body information monitoring.