We report a new method to fabricate a polypropylene (PP) nanowire array based triboelectric nanogenerator (TENG) with high output through structural control and surface functionalization for harvesting friction mechanical energy. Compared with the smooth PP film based TENG, the short circuit current (I_sc) and open circuit voltage (V_oc) of the PP nanowire based TENGs with the nanowire diameter of about 100 nm and length of about 14 μm increase by more than 4 times. More importantly, after surface functionalization with a modifier of 1H,1H,2H,2H-perfluorooctyltrichlorosilane, the output of the PP nanowire based TENG is further increased to a maximum V_oc of 1900 V and a short circuit current density of 19 mA/m², increased by more than 100 times than that of the flat PP film based TENG. This TENG can light up 372 commercial LEDs. Furthermore, a self-powered temperature sensor is designed, which shows great potential application in daily life. By taking this simple and effective surface modification strategy, we believe various materials could be used for energy harvesting by TENGs and other devices with high performance.