A typical frequency domain marine controlled-source electromagnetic (CSEM) system consists of a deep-towed electric dipole and an array of seabed receivers.Simulations of marine CSEM data often approximate the dipole source as an ideal horizontal electric dipole (HED).Actually, however, the transmitter will be rotated horizontally, tired vertically and deviated from the survey profile due to ocean currents.And free-fall receivers may be also rotated to some arbitrarily horizontal orientation and located on sloping seafloor.The errors in the position and orientation of the transmitter and receivers can propagate into errors on observation data.In this paper, the effects of errors in the transmitter tilt, transmitter rotation and transmitter deviation from the survey profile as well as receiver location and orientation on marine CSEM data are investigated.Simulations of one-dimensional models show that uncertainties of position and orientation of transmitter antenna have large effects at short offsets less than 1km.The transmitter altitude and inline displacement have largest effects on observed data.