The cockpit loudspeaker of civil aircraft is an electrical-acoustic transducer, which is installed in the aircraft cockpit. It can convert the electrical signal into an acoustic signal and radiate the acoustic power to the cockpit. Cockpit loudspeakers can not only provide communication voice between cabin crew and tower control personnel, but also provide navigation sound, Selcall voice and aural warning to pilot. It is an indispensable airborne device, which provides guarantee for flight safety. The squeal of cockpit loudspeaker is so unbearable that the pilots cannot hear other sounds, or even cannot use the voice communication system, which can seriously affect flight safety. This paper points out the harm of the cockpit speaker squeal, analyzes the cause of squealing. And on this basis, this paper discusses the inhibition method of the squeal, which provides some reference for the design of acoustic feedback inhibition of civil aircraft cockpit audio system.