BACKGROUND:　3-Methyl-3-penten-2-one　(3M3P)　is　an　indispensable　raw　material　used　for　the　synthesis　of　OTNE　(octahydrotetramethyl　acetophenone),　a　synthetic　ketone　fragrance　known　by　commercial　trade　names,　such　as　Iso　E　Super®,　which　is　one　of　the　most　important　ingredients　in　perfumes.　This　work　is　the　first　to　unravel　the　reaction　route　and　kinetics　for　the　synthesis　of　3M3P　via　the　cross-aldol　condensation　of　acetaldehyde　with　butanone,　catalyzed　by　the　heterogeneous　acidic　ion　exchange　resin　(NKC-9).　RESULTS:　An　effective　method　was　developed　to　evaluate　this　complex　reaction　system:　the　reaction　routes　were　determined　experimentally　from　the　product　structures　detected　by　Gas　Chromatography　Mass　Spectrometry　(GC-MS),　and　the　significance　of　side　reactions　were　evaluated　by　the　Yoneda　group　contribution　method.　The　major　side　reactions　are　the　self-condensation　of　acetaldehyde　(significant　even　under　optimized　reaction　conditions)　and　the　cross-aldol　condensation　of　acetaldehyde　with　3M3P　(which　could　be　effectively　suppressed　at　high　butanone-acetaldehyde　molar　ratio).　The　reaction　kinetics　was　investigated　at　temperatures　of　60–90　°C,　catalyst　mass　fraction　of　5　to　15%,　and　molar　ratio　of　5–20.　At　optimized　reaction　conditions,　the　yield　of　3M3P　was　up　to　90.85%,　which　is　2.4　times　higher　than　that　for　the　classic　homogeneous　catalysts　(yield　©　2020　Society　of　Chemical　Industry　(SCI)