Droop-controlled　parallel　inverters　are　widely　adopted　in　micro-grids　due　to　its　high　reliability　and　low　cost.　However,　the　interaction　among　the　inverters　will　cause　whole　system　to　be　unstable　even　though　each　individual　inverter　can　operate　stably　in　stand-alone　mode.　A　lot　of　work　has　been　done　for　analyzing　the　stability　of　parallel　inverters　with　droop　control　through　state-space　approach　originally　used　in　conventional　electrical　power　system.　For　this　existing　approach　it　is　necessary　to　have　the　knowledge　of　inside　parameters　of　each　individual　inverter　in　advance,　while　in　practical　applications　it　is　not　so　convenient　to　obtain　the　internal　structure　and　parameters.　To　overcome　this　problem,　this　paper　proposes　a　stability　analysis　approach　for　the　droop-controlled　parallel　inverters　based　on　the　terminal-characteristics　of　individual　inverters.　At　beginning,　the　terminal-characteristics　of　individual　inverter　with　droop　control　are　defined　in　system　synchronous　reference　frame　(SRF),　which　can　be　represented　by　the　transfer　function　between　output　current　and　output　voltage,　and　the　transfer　function　between　output　current　and　fundamental　angular　frequency.　Then　the　terminal-characteristics　of　the　whole　parallel　system　are　derived　out　with　the　ones　of　each　individual　inverter.　Furthermore,　a　stability　criterion　is　proposed　for　the　parallel　inverters　based　on　the　terminal-characteristics　of　each　individual　inverter　according　to　the　Generalized　Nyquist　Criterion.　Finally,　the　proposed　terminal-characteristics　and　stable　criterion　for　droop-controlled　parallel　inverters　are　verified　in　frequency　domain.