Based on the Lighthill aerodynamic acoustics equation， the sound field is mumerically simulated with the difference method，with different inner situation and Intensity of jet sound field．and the spread characteristic are educed．the position where acoustic intensity reaches the highest level is found．The result show that， the second cut place has the most intensity of jet noise，noise energy become strengthen whit enhance of inner situation and pressure difference， that provides fl foundation for acoustic examination and quantitative analysis of valve gas inner leakage．At the same time ball valve inner leakage is experimented by acoustic method， the result proves the correct of numerical simulation．
