For the purpose of getting a better understanding of failure mechanisms of rock fracturing due to construction perturbation inside the right rock slope of Dagangshan Hydropower Staion, a high precision microseimic monitoring system was installed and preliminary source location data have been investigated. The optimal design of microseimic monitoring network, especially the sensor array was investigated based on P method and Powell algorithm. The positioning accuracy of the system has been adjusted according to artificial fixed blasting tests. The testing results show that microseismic source location error is less than 10 m in the scope of the sensor array, which demonstrates the monitoring system deployed at the right slope has a high positioning accuracy. Signals from 112 microseismic events with moment magnitude ranging from -1.8 to -0.4 were recorded during its 2-month monitoring period. The cluster distribution of microseismic events can reflect directly the construction progresses such as the concentration of microseismicity inside the drainage tunnel at 1081 m level. The present study have significantly improved the understanding of the characteristics of the failure associated with excavation inside the rock slope, and will greatly benefit the potential sliding areas prediction and support of hazards in the phase of construction in future.