Abstract: This paper selected 281 earthquakes with M_L≥2.0 from 1 January 2009 to 25 August 2016 recorded by Hainnan seismic networks, and relocated the focal depths of the earthquakes by using PTD method. And then the Pb phase in Hainan area were analyzed by using the reduced travel time and the Pb phase velocity fitting are corroborated. As a result, the Pb phases are identified in Hainan island. The results show that, 57 Pb phases were identified from 52 of the 281 seismic events with phase velocities 6.68 km/s. Based on inversion of seismic wave travel time equation, the average depth of Conrad’s discontinuity in Hainan area is determined to be 21 km.