Aiming at the vibration and noise problem of DN100-PN63 steam vent valve at the opening degree from 0 to 60% in a chemical plant,based on detached eddy simulation and MÖhring acoustic analogy theory,Fluent and Actran softwares were used to numerically simulate the flow field and sound field of the valve with 40% opening degree in real working conditions,and the internal flow of the valve and the noise distribution inside and outside the valve were studied.Four improved structures were proposed and the flow field and sound field were studied in depth.The results show that there are several vortices inside the original valve;the high Mach number (Ma>0.2) area of valve internals and orifice plate accounts for about 90%,and there are supersonic flow areas,which is very likely to produce a large shock wave and shock noise;the noise of 1 m away from the valve and pipe reaches 116 dB(A),which has the characteristics of breedband frequency and obvious quadrupole sound source;compared with the original structure,the four improved valve internals promote the disappearance of vortex and have obvious noise reduction effect.