Abstract: The paper analyzed and summarized the electrical characters of coal mine goaf, and elaborated the basic theory and operating procedure of coal mine goaf detection by using controlled source audio-frequency magnetotelluric sounding method. The specific effect of the controlled source audio-frequency magnetotelluric sounding method in goaf detection was summarized by combining practical application of goaf detection. The results showed that controlled source audio-frequency magnetotelluric sounding method could accurately and effectively detect goaf and water logging range, which had a better reflection for the fluctuation of high resistance limestone top surface in Ordovician.