Abstract: Marine Controlled-Source Electromagnetic Methods (mCSEM)are used to measure sub- surface resistivity from seabed. The resistivity information can be integrated with seismic data to define whether a structure contains hydrocarbon or not. Deepwater drilling is very expensive, so CSEM is widely used by large oil companies in deepwater petroleum exploration. The performance of CSEM on a specific block is affected by many factors, including water depth, seabed topography, burial depth of the target, resistivity contrast between the target and surrounding rocks, thickness of the target, target's lateral scale, and other non-hydrocarbon high-resistivity anomalies near the target or in sallow burial depth. This paper analyzed all these factors and their affects to CSEM. Before CSEM data acquisition, it is crucial to evaluate all these factors with mathematic modeling. Once all these factors are fit for CSEM, the results shall be maximized.