During the development process, avionics system shall meet the system requirements, ensure system integrity, meet system safety objective. Also, avionics system is driven by regulatory, business requirement and commercial requirement. However, these requirements are mutually effected, which resulting the trade study to be the necessary activity in the avionics system development process. This paper firstly illustrates the necessary and importance of that apply the trade study in avionics system development process. Secondly, functions that trade studies are conducted in avionics system development process are illustrated. Third, analyze the process that trade study shall follow in. Lastly, an example of trade study analysis methodology called Utility Curve applied in avionics network and the advice of trade study during avionics development process was given.