Abstract: Forward modeling of quasi-P-waves (qP) in TI medium for practical application draw great attention in recent year. Lowrank two-step wave field extrapolation can eliminate the SV-wave artifacts interference, but the two-step method relies on a real-valued phase function and cannot use in large time step. For this reason, we propose qP wave one-step wave field extrapolation method based on Lowrank approximation, One-step method has the ability to handle complex-valued phase functions, we add velocity gradient term to the phase function, and successfully applied in TTI media qP wave forward modeling. By experiment shows: One-step wave field extrapolation has the advantage the traditional two-step process, no SV-wave artifacts. One-step method is more stable in the large time step, and can reduce computing costs. In the case of anisotropic, the one-step wave field extrapolation applies to any inclinations, and the result of wave field simulation is clear and accurate, with no instability.