Abstract: In order to study the influence caused by mechanical slope excavation on the stability of existing tunnel, the field measurement and numerical simulation are effective methods. The monitoring scheme is determined according to "highway tunnel design specification" (JTG D70-2004). We use M20 blasting vibration test instrument monitoring the vibration velocity, and make statistical analysis, and study the relationship between each measuring point’s vibration velocity and the construction schedule, and through numerical simulation studying the influence caused by slope mechanical excavation on the deformation and stress of tunnel surrounding rock and. Research shows that: the greater the distance to source is, the smaller the vibration velocity is , and generally not more than 0.79cm/s, and vibration velocity is mainly between 0.01cm/s and 0.3cm/s. Slope mechanical excavation has less influence on the existing tunnel. Due to sloping relief effect, the existing tunnel has the trend of moving upper and left, but it is very small, and provides a reference for similar construction projects.