We　proposed　a　simple　and　efficient　modular　single-source　surface　integral　equation　(SS-SIE)　formulation　for　electromagnetic　analysis　of　arbitrarily　connected　penetrable　and　perfectly　electrical　conductor　(PEC)　objects　in　2-D　space.　In　this　formulation,　a　modular　equivalent　model　for　each　penetrable　object　consisting　of　the　composite　structure　is　first　independently　constructed　by　replacing　it　by　the　background　medium,　no　matter　whether　it　is　surrounded　by　the　background　medium,　other　media,　or　partially　connected　objects,　and　enforcing　an　equivalent　electric　current　density　on　the　boundary　to　remain　fields　in　the　exterior　region　unchanged.　Then,　by　combining　all　the　modular　models　and　any　possible　PEC　objects,　an　equivalent　model　for　the　composite　structure　can　be　derived.　The　troublesome　junction　handling　techniques　are　not　needed　and　nonconformal　meshes　are　supported.　The　proposed　SS-SIE　formulation　is　simple　to　implement,　efficient,　and　flexible,　which　shows　significant　performance　improvement　in　terms　of　CPU　time　compared　with　the　original　SS-SIE　formulation　and　the　PoggioMiller-Chang-Harrington-Wu-Tsai　(PMCHWT)　formulation.　Several　numerical　examples　including　the　coated　dielectric　cuboid,　the　large　lossy　objects,　the　planar　layered　dielectric　structure,　and　the　partially　connected　dielectric　and　PEC　structure　are　carried　out　to　validate　its　accuracy,　efficiency,　and　robustness.