Abstract: To analyze several key problems about effectiveness analysis of spaceborne parasitic SAR system，firstly,an index system ofefectiveness assessment is established based on the m ission request ofdistributed SAR system；combined with orbit characteristics of distributed small satellites，the model of system capability is established；based on system working state，Markov model of system reliability is established；based on capability model and reliability model，the model of effectiveness assessment is established．The simulation results indicate the proposed models provide theoretic dependence for effectiveness analysis of spaceborne parasitic distributed SAR system.