Breath group generally refers to one of units of speech production. It is an integral component of structural and contextual features of utterances with some responsibility for fluctuations in speech intelligibility. The purpose of this study was to know the characteristics of breath group in reading passages spoken by healthy speakers, specifically in view of aerodynamic aspects. Eighteen female speakers aged from 20 to 30 years old without communication problems and in healthy condition were participated in this study. PAS (Phonatory Aerodynamic System) was used for aerodynamic measurement of breath group. Results showed that the mean value of breath group in reading tasks was 16.03 per minute (SD=3.1), and the spoken syllables per one breath group were 17.95. And the mean time (m) of breath group was 3.06 (SD=0.62), and the ratio of exhalation and inhalation was appeared in the 1:5. The results need to be discussed in values of normality of breath group and clinical viewpoint, especially their potential implication from speech intelligibility caused by brain damage.