A low threshold nanolaser that contains nanowires, air gap and semicircular-top metal nanoridge structure was proposed.Through the finite element method to model characteristics and the quality of the laser gain factor and threshold for numerical calculation, the characteristic factor was studied with the geometric parameters (air gap, metal ridge width and nanowire radius) change. The results show that the property of the laser is optimized by adjusting the parameters. Under the optimal parameters, the gain threshold can reach 0.47 μm-1 and the transmission loss is only about 0.018. This shows that the nanolaser structure can achieve low threshold sub wavelength lasing and low loss transmission. It has a wide application prospect in the fields of biomedicine, optical communication etc. It provides technical support for miniaturization and integration of nano devices.