Abstract:Regarding the data picking-up difficulty when using seismic reflection travel-time tomography in velocity modeling for complex media,the theoretical analysis of the cause for the difficulty is conducted in this paper.The author believes that the introduction of the reflection horizon in modeling description caused the difficulty.In order to overcome the difficulty the new modeling description method and inversion object function were applied in this paper,seismic wave propagation direction and travel time were taken as the input for the inversion,the picked-up seismic wave propagation direction was used to constrain the ray path,so the uniqueness of the ray path was assured,at last it was not needed to define the seismic reflection horizon for the model.In order to validate the effectiveness of the new method,test calculation was carried out with Marmousi model,the test results show that the new method can in a certain extent overcome the difficulty which is often encountered in velocity modeling in complex media.