With the methods of spectral analysis of vibration signals and numerical simulation of blasting vibration, influence of the blast-created free surfaces on vibration frequency during underground full-face excavation were investigated in the present study. The vibration signals were measured from a specially designed small-scale blast test, where blastholes were detonated under different free surface conditions. The results show that the presence of free surfaces results in higher vibration frequency and an increased proportion of high-frequency vibration energy to total energy. As distances between blasting sources and the free surfaces decrease, the vibration frequency increases. This is since the rarefaction waves reflected on the free surfaces are superimposed onto the blast-induced initial compressive stress waves, and it causes the rising time and duration of the far-field blast loading pressure becomes shorter, thereby leading to an increased frequency of the loading. From the view of vibration frequency, the damage of blasting vibration to structures can be mitigated by a better free surface condition. Reliability of the results is demonstrated by the vibration monitoring in the blast test.