The physical properties of nano-thickness membrane are known to be different from those of bulk material. However, it requires a novel approach to measure the physical properties of nano-thickness membrane due to its nano-scale dimension. Currently, many potential applications for the nanoscale structures are not really practical because their mechanical properties have not been established. In this study, a suspended high aspect ratio silicon nitride nano-thickness membrane is fabricated by using silicon micro-machining. The membrane has a thickness of 30 nm and an area of 4 mm by 7 mm, as shown in Fig.1. Young's modulus of the silicon nitride nano-thickness membrane is determined from the deflection of the suspended membrane, which is resulted from the weight of membrane itself.