Because the accuracy and the fluency are the essence in English speaking, both of them are very important in English trencher training and in-service English training programs. To get the accuracy and the fluency, the causes and the phenomena of the unnatural pronunciation have to be diagnosed. Consequently, the problematic and unnatural pronunciation of Korean elementary and secondary English teachers should be analyzed with using Acoustic Analyzing tools like CSL, Multi-speech and Praat. In addition, an attempt to Pinpoint what the causes of unnatural pronunciation was executed. Next a procedure and steps were proposed for in-service training programs that would cultivate the fluency and the accuracy. In case of elementary teachers, the unnatural pronunciation of segmental features and suprasegmental features were found much. therefore segmental features should be emphasized in the begging of pronunciation training courses and then suprasegmental features have to be emphasized. In case of secondary teachers, the unnatural pronunciation of suprasegmental features were found much. Therefore segmental and suprasegmental features have to be focused at the same time. In other words, features in word level should be focused first for elementary English teacher, and features in word level and beyond word level should be trained at the same time for secondary English teachers.