Ngong tunnel， which is designed for single track railway tunnel， is located in the Great Rift Valley. It has 4 507 meters long，and it is the control engineering of the railway from Nairobi to Malabar. The surrounding rock of Ngong tunnel is mainly basalt in the III and IV levels. The drilling and blasting tunnel is excavated by bench excavation. We obtain the attenuation law of blasting vibration considering the dispersion by blasting vibration test and data analysis for evaluating the influence of blasting damage of Ngong tunnel on surface structures. According to this， we develop the safety evaluation of the influence of blasting damage of surface structures along the Ngong tunnel. The research achievements provide a scientific basis for blasting working and safety control of Ngong tunnel.