Migration imaging technique is commonly used in reconnaissance beyond tunnel or roadway,of which the important part is the travel time calculation.Because the imaging area approximates the whole underground space,such non-penetrating bodies as tunnels or roadways,holes,and mine goaves have a great influence on the travel time of seismic wave.Therefore,based on Fast Marching method (FMM),the authors developed a new algorithm to calculate the travel time of seismic waves for those complex models including the non-penetrating bodies.In this algorithm,a labeling technique is adopted for non-penetrating bodies,and the ray will automatically avoid and bypass the non-penetrating bodies in narrow band of FMM when a ray approaches them,making the seismic wavefront propagation more realistic.Also,this new algorithm can be applicable to the model for irregular ground surface if the above surface area is regarded as a non-penetrating body.Therefore,the new algorithm can deal with the model with non-penetrating bodies and irregular ground surface simultaneously.Compared with the conventional algorithm,the marked point is the only change of the developed algorithm,which maintains the accuracy and efficiency of FMM.The numerical test results show that the improved algorithm can calculate the travel time accurately,and has strong adaptability and good stability to complex model.