Among the WBG semiconductors, b-Ga2O3 is considered a promising material because it exhibits superior UV photodetection performance. There is a broad spectrum of solar-blind PD based optoelectronic applications in which UV detection and mechanical flexibility are simultaneously needed, such as wearable UV monitors. Therefore, the development of a freestanding and flexible form of b-Ga2O3 nanomembranes (NMs) would directly benefit numerous future applications that require the combined advantages of rigid PDs such as high photoresponsivity and sensitivity and those of flexible ones such as good mechanical bendability and durability. This team reported the fabrication of b-Ga2O3 NM based flexible PDs and the investigation of their optoelectrical properties under bending conditions. Flexible b-Ga2O3 NM PDs exhibited reliable solar-blind photo-detection and optical properties were measured under different strain conditions. The results of a multiphysics simulation and a density-functional theory calculation showed that the conduction band minimum and the valence band maximum states were shifted nearly linearly with the applied uniaxial strain. It was found that nano-gaps in the b-Ga2O3 NM play a crucial role in enhancing the photoresponsivity of the b-Ga2O3 NM PD under bending conditions due to the secondary light absorption caused by reflected light from the nano-gap surfaces. This research provides a viable route to realize high-performance flexible photodetectors, which are one of the indispensable components in future flexible sensor systems.