Secondary　electron　(SE)　emission　(SEE)　from　material　surfaces　is　a　frequent　phenomenon　in　space　and　vacuum　environments.　SEE　modulation　is　important　since　it　governs　the　performance　of　some　devices　such　as　electronic　multipliers　or　induces　some　detrimental　effects　such　as　multipactors.　Surface　coating　has　been　reported　to　modulate　SEE　effectively,　whereas　SEE　behaviors　of　coating　structures　are　not　clearly　understood　yet,　and　the　appropriate　theory　to　describe　SEE　characteristics　quantitatively　for　coating　structures　is　less　developed　so　far.　Here,　we　have　prepared　four　alumina　coatings　possessing　various　thicknesses　to　research　the　SEE　characteristics　of　coating　structures　and　have　shown　how　the　coating　thickness　affects　the　SEE　behaviors.　Besides,　by　considering　coating/substrate　as　an　ideal　double-layer　structure,　we　have　derived　several　equations　to　describe　the　producing,　transmitting,　and　escaping　processes　of　excited　inner　SEs　and　finally　constructed　a　unidimensional　SEE　model　for　double-layer　structures.　The　model　is　applicable　to　reveal　the　dependence　of　trueSE　yield　(TSEY)　on　the　top　and　bottom　layers＇　physical　properties　and　estimate　TSEY　proportions　contributed　by　the　top　and　bottom　layers　at　random　energy　points.　By　employing　the　concept,　SEE　characteristics　of　Al2O3/Si,　MgO/Si,　and　TiO2/Si　double-layer　structureshave　been　quantitatively　interpreted.　Moreover,　the　abnormal　SEY　curve　with　a　double-hump　shape,　which　is　induced　by　the　peak　position　distinction　of　SiO2/Si　structures,　can　also　be　explained.　This　work　is　of　great　significance　to　comprehend　TSEY　modulating　regularities　of　various　double-layer　structures　applied　in　surface　engineering.　©　2021　Author(s).