[en] Highlights: • The piezoelectric coefficient of this flexible piezoelectret generator reached ~ 6300 pC/N. • The generator generated peak power of ~ 0.444 mW and worked steadily for ~ 90000 cycles. • The generator worked steadily under extreme moisture and temperature up to 70 °C. Stable and repeatable operation is paramount for practical and extensive applications of all energy harvesters. Herein, we develop a new type of flexible piezoelectret generator, which converts mechanical energy into electricity consistently even under harsh environments. Specifically, the generator, with piezoelectric coefficient (d₃₃) reaching ~ 6300 pC/N, had worked stably for continuous ~ 90000 cycles, and the generator pressed by a human hand produced load peak current and power up to ~ 29.6 μA and ~ 0.444 mW, respectively. Moreover, the capability to steadily produce electrical power under extreme moisture and temperature up to 70 °C had been achieved for possible applications in wearable devices and flexible electronics.