This paper reports the successful distribution of entangled photon pairs over a distance of 1203 kilometers using a satellite-based system. The experiment, conducted by a team from the University of Science and Technology of China and other institutions, involved a satellite named Micius, which was launched into a sun-synchronous orbit at an altitude of 500 kilometers. The satellite communicated with two ground stations, Delingha and Lijiang, located 1203 kilometers apart, through two downlink channels with a total length ranging from 1600 to 2400 kilometers. The system demonstrated the survival of two-photon entanglement and a violation of Bell's inequality by 2.37 ± 0.09, under strict Einstein locality conditions. The effective link efficiency at 1200 kilometers was over 12 orders of magnitude higher than the direct bidirectional transmission of the same photons through commercial telecommunication fibers with a loss of 0.16 dB/km. The study highlights the potential of satellite-based quantum communication for long-distance quantum networks and quantum information protocols.This paper reports the successful distribution of entangled photon pairs over a distance of 1203 kilometers using a satellite-based system. The experiment, conducted by a team from the University of Science and Technology of China and other institutions, involved a satellite named Micius, which was launched into a sun-synchronous orbit at an altitude of 500 kilometers. The satellite communicated with two ground stations, Delingha and Lijiang, located 1203 kilometers apart, through two downlink channels with a total length ranging from 1600 to 2400 kilometers. The system demonstrated the survival of two-photon entanglement and a violation of Bell's inequality by 2.37 ± 0.09, under strict Einstein locality conditions. The effective link efficiency at 1200 kilometers was over 12 orders of magnitude higher than the direct bidirectional transmission of the same photons through commercial telecommunication fibers with a loss of 0.16 dB/km. The study highlights the potential of satellite-based quantum communication for long-distance quantum networks and quantum information protocols.