The installation of an appropriate slender-rod on the nose of supersonic aircraft is able to reduce flight noise level. Based on Fluent quasi three-dimensional numerical simulation method in this paper, 24 groups of slender-rod models are simulated and analyzed and compared in influence on the far-field pressure, to compare noise reduction effect of various slender-rod and summarize effective noise reduction model. Furthermore, from the theory of aerodynamics ,this paper explains the solution of numerical simulation ,and revealing inner relation between the slender-rod noise reduction effect and slender-rod shape. Besides, this paper analyze the influence of slender-rod to the sonic boom from the aspects of the far-field pressure maximum and curve shape etc. The results show that single-stage conical slender-rod with 6 meters length and 12.5 degrees half- cone angle has obvious effect in noise reduction; reasonable multistage conical slender-rod significantly reduces the initial overpressure value, and delay the far-field pressure peak ;concave-concave type, concave-cone type, convex-concave type and convex-cone type slender-rods greatly reduce the far-field pressure peak value and improve the shape of pressure curve and have More significant noise reduction effect ; strong expansion wave produced by slender-rod can significantly weaken the nose shock wave in the process of shock wave propagation, thereby weakening the sonic boom.