HRG(Hemispherical Resonator Gyro) is a new kind of solid state vibratile gyro with high-precision, high-reliability and long-life. The resonant frequency’s change with the temperature will have a disadvantageous effect on Gyro’s control precision . The basic control principle of HRG is introduced in this paper, and a DPLL based on the Cordic algorithm is proposed. The Cordic algorithm principle and the design method on FPGA have been given. The simulation with Modelsim shows that the frequency precision is 0.004 6 Hz and the phase precision is 0.06°,when the system main clock is 20 MHz. The efficiency of FPGA with 7.2 ten thousands gates is 65% . The results of performance test show that the slow frequency DPLL realize the function of accurate following the slow change of HRG’s vibratile frequency and phase from 4.5 kHz to 5 kHz.