Asteroids are considered to be among the most primitive celestial bodies in our solar system and are crucial for understanding the origin and formation processes of the solar system. Furthermore, the significance of asteroids has been increasingly recognized, both in terms of planetary defense and possible space resource utilization. Astronomical observations have been one of the most powerful methods to investigate the physical properties of asteroids, enabling us to obtain information such as orbit, size, shape, spin state, and surface properties. In this talk, I will introduce an overview of how astronomical observations have been used to study the physical properties of asteroids. Specifically, I will present the outcomes of large-scale survey observations and discuss the synergistic effects of utilizing the observation results from various surveys. Additionally, I will present the interplay between space missions and astronomical observations in asteroid research, highlighting their complementary roles and the unique benefits each approach provides.