The formulation of a proper velocity analysis flow is a prerequisite for implementation of high-precision reverse time migration (RTM), and the choice of migration parameter influences the image result directly as well. Traditional means usually construct a velocity model by interpolating along the layer. The author introduced a 3-step method to construct a more accurate velocity model, and applied it to field data for migration. The result indicates that this 3-step method is capable of eliminating the fault structure and obtaining more reliable image especially for the detailed structure of the salt dome. Besides, the migration parameters are discussed in this paper, including the main frequency of the wavelet, the migration aperture and the grids size for migration. The test in northern Africa shows that the optimization of those parameters helps reduce the problems of inaccurate image, low S/N, numerical dispersion and high computational cost, thus achieving accurate salt dome imaging.