Abstract: The basic principle of the transient electromagnetic methods (TEM) in goaf exploration was introduced. Combined with realistic problems in Fusun east open-pit mine which goaf cause the serious influence on safety production，old mining area of the north slope in open-pit mine was explored by TEM. According to the detection results，the dangerous abnormal area was determined. It avoids losses from the blind drilling，and it provides scientific basis for safety mining design and safety control of the open pit.

Key words: TEM, Basic principle, Exploration, Safety production