In the ultrasonic assisted drilling of titanium alloy machining, to solve the problems of system detuning, amplitude attenuation and even vibration loss after the load is applied to the acoustic system, the theoretical and experimental research on the force load of acoustic system is carried out. The four-terminal network method is used to unify the transducer, the composite horn and the load, and the overall theoretical model of the ultrasonic drilling acoustic system is established. The ANSYS commercial software package is used to simulate the acoustic system with static and dynamic drilling forces. The design covered the mechanical (force-loading) test and actual drilling processing experiment, explored the force load effect on the system characteristics. It is proved that a rise in the force load increases the system input impedance, shifts the resonance frequency, and reduces the system amplification factor. In the ultrasonic drilling of titanium alloy processing, the current is increased by more than 60%, and when the frequency variation/shift exceeds 350Hz, the acoustic system will exhibit significant detuning, which, in turn, will deteriorate the system stability. The research results have certain guidance and reference significance for ultrasonic assisted drilling.