Space-borne Synthetic Aperture Radar (SAR) has emerged as a pivotal technology in remote sensing, offering high-resolution radar images irrespective of weather conditions and daylight availability. The quality of SAR images is crucial for its application in various domains, including disaster monitoring, target identification, and military reconnaissance. This paper mainly discusses some quantitative indicators of SAR image quality (including the definition of these indicators, physical meaning, and its measurement method in practice). It delves into the fundamental principles of SAR technology, outlines the key quality metrics, and discusses both subjective and objective assessment methods. Furthermore, this paper concludes with a discussion on emerging trends and future directions for SAR image quality assessment methods.