Sensing principles and characteristics of some optical electric-power sensors are reviewed, and some typical problems, solutions, and research proposals are summarized and analyzed. Main advantages of optical electric-power sensors include large measurement range, broadband frequency response, and good electrically insulating capability. Optical electric-power sensors can be classified into two types according to different light modulating approaches, i.e. direct modulation and indirect modulation. Compared with conventional optical voltage and current sensing signals, the optical electric-power sensing signal is much weaker and the active power sensing signal is a direct current signal. It is difficult to distinguish the direct current sensing signal from fluctuation of the probing light intensity. The sensing material of a single crystal-based electric-power sensor should exhibit both electro-optic and magneto-optic effects, or dual transverse electro-optic Pockels or Kerr effects. In addition, we should consider multiple optical effects in sensing crystals and their mutual interference, and how to avoid or suppress the temperature drift of sensing signal. Optical electric-power sensors have potential applications to smart power grid, microwave and electro-magnetic pulse power measurement.