Abstract: With offshore HC exploration and development changing from shallow water to deep water, offshore controlled source electromagnetic technology (CSEM) has been widely used in deep water exploration to reduce exploration risk. Because of the poor conductivity of hydrocarbon, the resistivity of HC bearing rocks is higher than the water-bearing rock. With CSEM exploration techniques, the abnormal body with high resistance can be identified from the low resistance background. The risk of drilling can be reduced greatly through interpretation of CSEM data and seismic data. In this article, the basic principles, the operation ways and the factors which might influence the exploration results are discussed, and the exploration results of CSEM have been compared with the results of seismic exploration. The aim of this article is to provide reference for the selection of deep water HC exploration and development methods.