We　report　an　analytic　model　for　quantitatively　calculating　the　transmission　attenuation　of　single-wall　hollow-core　anti-resonant　fibers.　Our　calculations　unveil　the　light　leakage　dependences　on　azimuthal　angle,　polarization,　and　geometrical　shape　and　have　been　examined　in　a　variety　of　fiber　geometries.　Based　on　our　model,　a　simple　and　clear　picture　about　light　guidance　in　hollow-core　lattice　fibers　is　presented.　Formation　of　equiphase　surface　at　fiber＇s　outermost　boundary　and　light　emission　ruled　by　Helmholtz　equation　in　transverse　plane　constitute　the　basis　of　this　picture.　Using　this　picture,　we　explain　how　the　geometrical　shape　of　a　single-wall　hollow-core　fiber　influences　its　transmission　properties.　(C)　2014　Optical　Society　of　America