Biodegradable polymers (BPs)-based triboelectric nanogenerators (TENGs) have advantages, including biocompatibility and biodegradability. However, biodegradable TENGs (BD-TENGs) possess relatively low output performance, limiting their application due to the small differences in triboelectric polarities for most BPs. Molecular doping is a simple and effective method in altering the triboelectric polarity of triboelectric materials and improving the output performance of BD-TENGs. However, there is a lack of laws and mechanism about the differences in triboelectric polarities of different doped molecules, especially of molecules with biodegradability and biocompatibility. Here, kinds of doping molecules are selected for doping in tribopositive and tribonegative materials, respectively, and their triboelectric polarities and related laws are researched. In particular, the output performance of BD-TENG is improved several times by doping small amounts of poly (propylene glycol) (PPG) and ethyl cellulose (EC), with enhanced resolution in abnormal respiratory signal monitoring. This work not only provides theoretical guidance for the selection of triboelectric molecules but also conducts in-depth research in molecular-level triboelectric mechanisms.