In the present study, the effect of the electromagnetic field, induced by radio frequency (RF) coils and coupled with the pelvic tissues, was calculated with the method of finite difference time domain (FDTD). Using the established electromagnetic model of human pelvis region, the simulation was implemented. The imaging uniformity was quantitatively calculated and scaled with the values of the percentage image uniformity (PIU). The electromagnetic model was derived from the anatomical data of human pelvic region and loaded into the simulation. The results showed that the homogeneity of the magnetic fields was severely damaged due to the coupling between the RF coil and the human tissues when loaded with the human pelvis in the Birdcage RF coils at 3T. The research results set a basis meaningful for the design of RF coils.