At present, the link budget of satellite systems has become an essential part of the engineering design of satellite communication systems. Through the link budget, the performance of communication equipment and the loss of signal attenuation and interference during transmission can be comprehensively analysed, and the equipment resource configuration and device parameters can be continuously optimised to meet the user's communication capacity and quality requirements while leaving appropriate margins. This study aims to explore the link budget of the satellite system, study the parameters, channel characteristics and application of the satellite link budget, and provide a theoretical basis and practical reference for the design and performance optimisation of the satellite communication system. Firstly, the research background and significance of satellite communication links are introduced, and the characteristics and advantages of other communication systems are analysed and compared from multiple dimensions. The main factors affecting the link budget, such as path loss, related atmospheric attenuation, and carrier-to-noise ratio, were mainly discussed using the parameter estimation method and comparative analysis. Then, from the perspective of channel characteristics, the critical issues of satellite link budget, including signal-to-noise ratio, code rate and other factors, are discussed. Based on the above research, this paper summarises the performance evaluation of satellite communication systems and provides a reference for practical applications.