Optimal design of nuclear magnetic resonance (NMR) logging device sensor can enhance its detection performance and improve signal-to-noise ratio, and the accuracy of results from numerical method is absolutely critical for optimal design. In this paper, an eccentric NMR logging device static field distribution and radio frequency field distribution are simulated by the electromagnetic finite element method, and the influences of model shape, model size and element shape on simulation results are analyzed. A comparison between the measurements and simulation data indicates that they are in good agreement with each other. In the design process of NMR logging device sensor, by choosing a circinal model which is similar to the shape of borehole, setting model size to be 10-15 times the sensor diameter, and adopting triangle element, the accuracy of numerical simulation can be improved and the reliability of optimization design can also be enhanced.