Implicit finite-difference (IFD) extrapolation operator and plane wave migration in TTI media are studied in this paper. Compared to isotropic and VTI media, the dispersion relation of TTI media is much more complicated. It is difficult to get the explicit expression of the dispersion relations. It needs no longer only a symmetrical even function like isotropic and VTI media but also an odd function to express the dispersion relations. We design TTI medium IFD wave-field extrapolation operator and solve operator coefficients by nonlinear optimization method. We combine the theory of plane wave migration in isotropic media with the IFD operator in TTI media and extend plane wave migration to TTI media. Comparing the dispersion curves and migration impulse response of the IFD extrapolation operator with the theoretical solution verifies the high accuracy of the operator. Synthetic P-wave data from full elastic TTI equation modeling followed by polarization analysis verifies the accuracy and effectiveness of the method.