Achievement of p-n homojuncted GaN enables the birth of III-nitride light emitters. Owing to the wurtzite-structure of GaN, piezoelectric polarization charges present at the interface can effectively control/tune the optoelectric behaviors of local charge-carriers (i.e., the pitzo-phototropic effect). Here, we demonstrate the significantly enhanced light-output efficiency and suppressed efficiency droop in GaN microwire (MW)-based p n junction ultraviolet light-emitting diode (UV LED) by the piezo-phototronic effect. By applying a 0.12% static compressive strain perpendicular to the p n junction interface, the relative external quantum efficiency of the LED is enhanced by over 600%. Furtherinore, efficiency droop is markedly reduced from 46.6% to 7.5% and corresponding droop onset current density shifts from 10 to 26.7 A cm72. Enhanced electrons confinement and improVed holes injection efficiency by the piezo-photottonic effect are revealed and theoretically Confirmed as the physical mechanisms. This study offers an unconventional path to develop high efficiency, strong brightness and `high power III-nitride light sources.