Abstract: This paper discribes the noise sources of machine tools and the methods of noise spectral analysis. Gear drive is usually considered as the main source of machine tool noise, however it is by no means always unique. Besides the gears, thcre are a lot of element affecting maehine tool noise, such as, electrical motors, bearings, belts, unbalanced high speed spindles and constructional vibration and so on. The most important noise source of a specific can only be identified by means of noise spectrum analysis. Taking the type YN-01 lathe (φ400mm) and type T649 boring-milling machine as example, this article presents the experimental results obtained by using various kinds of noise reduction measures, which include mainly: ( 1 ) contral the constructional vibration of gear box, by adding suitable reinforcing ribs, ( 2 ) balance the high speed spindle and the motor shaft, ( 3 ) increase the machining accuracy of gears, ( 4 )reduce gear noise through tooth chamfering and damping, ( 5 ) improve the constructional design, ( 6 ) improve the quality of assembling. Finally some rules for designing low noise machine tools has been laid and considered as the foundamental apprach to Control machine toal noise.