The invention provides a noise reduction method, a method for extracting phonetic feature, a speech recognition method and a speech model training method as well as a noise reduction device, a device for extracting phonetic feature, a speech recognition device and a speech model training device. According to one aspect of the invention, the noise reduction method which is used in speech spectrum containing noise includes the following steps: according to a noise estimation spectrum, logarithm spectrum minimum mean square error estimation of the speech spectrum is completed to reduce the noisecontained in the speech spectrum, wherein, the logarithm spectrum minimum mean square error estimation is realized through calculating gain function according to the following steps: the gain function is calculated through Taylor series accumulation and numerical integration; finally, the result of the Taylor series accumulation is combined with that of the numerical integration.