Abstract: Aiming at the inversion of velocity model of irregular geological body, this paper proposes a method of combining geological model with travel-time tomography based on body-fitted grid generated by transfinite in-terpolation.First, the body-fitted grid is used to describe the irregular geological body.On the basis of the grid construction, the shortest path method is used to obtain the travel time and ray path from the source to the receiver.Then, according to the travel time and ray path, the back-projection method (BPT) combined with the damped least square method (DLSQR) is used as the travel time inversion method.By the travel time inversion iteration, the velocity model is finally obtained.The whole process is programmed in Matlab, and 10% Gaussian noise is added to the first arrival of the theory.The final numerical simulation verifies the results.The numerical results show that the difference between the theory of 97.5% grid element and the inversion velocity is within ±300 m/s, and the corresponding relative error is within 6.35%.The theoretical velocity and inversion velocity are basically the same, and the high and low velocity regions are well-defined and the inversion results are good.This provides a new method for the inversion of velocity in complex irregular geology.