In order to evaluate the effects of electromagnetic fields (EMF) of ultra high voltage (UHV) transmission lines exposure on important life organs and tissues of BALB/c mice, an exposed environment was constructed in laboratory. Fifty male adult BALB/c mice were divided into two groups. One group has been done by daily exposures of 24 hours, and the other sham-exposed group served as the control. After six weeks of exposure, all the mice were sacrificed. The important life organs of BALB/c mice in vivo were screened with serum biochemical assay, morphological observation at histological and ultrastructural levels as well as flow cytometric analysis (FCM). There were no significant differences in important organs and tissues except testis germ cells and bone marrow between exposed groups and control groups.