Abstract: Power frequency electromagnetic field is an extremely low frequency, usually 50 Hz or 60 Hz, electromagnetic field produced by different levels of power lines and electric appliances. In order to prevent its adverse health effects, many countries and organizations have established its exposure limits. The current exposure limits set by different institutions were summarized here, and the rationales and characteristics of them were analyzed. The variations of these different exposure limits were introduced and discussed, and the controversy focused on the exposure limit was also presented.