A satellite-to-ground quantum key distribution (QKD) experiment was conducted over a distance of up to 1200 km using a low-Earth-orbit satellite named Micius. This experiment demonstrated a high-efficiency QKD link with a key rate of over kHz, significantly outperforming fiber-based QKD. The satellite, launched in 2016, used a decoy-state QKD transmitter at 850 nm wavelength and a ground station in Xinglong, China, to establish a secure quantum communication link. The experiment overcame challenges such as atmospheric turbulence, beam diffraction, and pointing errors through advanced tracking and pointing systems. The satellite-to-ground link achieved a quantum bit error rate (QBER) of about 1.1%, consistent with expected background noise levels. The experiment also demonstrated the feasibility of using satellites for global-scale quantum networks, with the potential to enable secure key exchange between distant locations. The results showed that satellite-based QKD is significantly more efficient than fiber-based QKD, with a channel efficiency that is 20 orders of magnitude higher at 1200 km. This experiment marks a key milestone in the development of global quantum networks.A satellite-to-ground quantum key distribution (QKD) experiment was conducted over a distance of up to 1200 km using a low-Earth-orbit satellite named Micius. This experiment demonstrated a high-efficiency QKD link with a key rate of over kHz, significantly outperforming fiber-based QKD. The satellite, launched in 2016, used a decoy-state QKD transmitter at 850 nm wavelength and a ground station in Xinglong, China, to establish a secure quantum communication link. The experiment overcame challenges such as atmospheric turbulence, beam diffraction, and pointing errors through advanced tracking and pointing systems. The satellite-to-ground link achieved a quantum bit error rate (QBER) of about 1.1%, consistent with expected background noise levels. The experiment also demonstrated the feasibility of using satellites for global-scale quantum networks, with the potential to enable secure key exchange between distant locations. The results showed that satellite-based QKD is significantly more efficient than fiber-based QKD, with a channel efficiency that is 20 orders of magnitude higher at 1200 km. This experiment marks a key milestone in the development of global quantum networks.