Abstract: Three methods in this paper were used to determine the focal depth of the Changli M_L4.5 earthquake in Hebei, which were CAP, TDMT and sPL depth seismic phase. First, the focal mechanical solution of Changli earthquake was obtained by using CAP method, and the optimum focal depth was 4.5 km. Then the fitting focal depth range was 5 ~ 6 km by using TDMT method. Finally, the waveform data of the stations within the range of 20 ~ 80 km from the epicenter were processed, and the sPL seismic phase was identified at two stations, CHL station and BDH station. Based on the focal mechanism solution, the theoretical waveforms corresponding to the 1 ~ 16 km depth range were calculated, and by the comparison with the observation waveform, the focal depth was 5 km. The depth research results of the three methods are basically the same, and combined with the focal scale of the Changli M_L4.5 earthquake and calculation results of the Changli M_L3.9 earthquake by CAP and sPL phase, it shows that the focal depth of the Changli M_L4.5 earthquake should be 4 ~ 6 km.