A quench protection system has been proposed for an 8-T split superconducting magnet consisting of low-temperature superconducting (LTS) NbTi coils and high-temperature superconducting (HTS) Bi2223 coils. For the LTS coils, a code has been developed to adjust the circuit parameters and the heater geometry. The calculation method of the internal electric potential in the LTS coil is introduced. For the HTS coils, the temperature and current margins are studied. The voltage signal for quench detection is chosen, and quench simulations on the HTS coil with different heating fluxes and heating zones are performed. The simulation results show that the employment of only the dump resistors can bring down the current and the temperature rise rapidly in the event of a quench. The coupling effect of the LTS and HTS coils is simulated and analyzed.