To solve the problem of optical handling of microwave signal in satel lite communication, the inter-satellite microwave photonic frequency down conversion system is mode led,two parallel dual-electrode Mach-Zehnder modulators based on optical carrier suppression mo dulation are utilized to modulate the uplink microwave signal received by satellite and the l ocal oscillator signal produced in satellite,respectively,and the microwave signal is optically amplifi ed,transmitted and frequency-down converted in the inter-satellite optical link.The output signal and noise of system are analyzed with Bessel expansion,the local oscillator signal power is optimiz ed,and the effects of modulator bias phase drift,phase shifter error and emission optical power on the system performance are simulated.The results show that the deterioration o f output carrier to noise ratio(CNR) is under 0.05dB while the mod ulator bias phase drift is less than 5℃,the output CNR deterioration is under 0.02dB while the phase shifter error is less than 5℃,and the frequency down conversion system has high stability.When the emission optic al power is 10.48dB, the system output CNR is 31.33dB,which can meet the practical requirement.The inter-satellite microwave photonic frequency down con version system can be applied to the optical handling of microwave signal in the future satellite optical communications.