The　combustion　characteristics　and　cycle-by-cycle　variations　of　a　spark-ignition　engine　fueled　with　pure　methanol,　ethanol,　and　n-butanol　were　comparatively　analyzed.　All　experiments　were　performed　using　a　natural　gas/alcohols　dual-fuel　engine　with　the　alcohol　fuel　energy　substitution　ratio　of　100%.　The　engine　was　kept　under　a　low　load　with　a　brake　mean　effective　pressure　of　0.387　MPa.　Engine　speed　was　kept　constant　at　1600　r/min　and　air–fuel　ratio　(λ)　was　set　in　the　range　of　1–1.5　and　varied　in　intervals　of　0.1.　The　results　showed　that　the　pure　methanol　fuel　yielded　the　highest　peak　cylinder　pressure　(Pmax)　and　peak　heat-release　rate　(HRRmax)　of　the　engine,　followed　by　ethanol　and　then　n-butanol.　Moreover,　Pmax　and　HRRmax　decreased　with　the　increase　in　λ,　and　the　corresponding　crank　angles　were　reduced　for　the　three　primary　alcohol　fuels.　The　flame-development　and　flame-propagation　periods　of　methanol　were　shorter　than　those　of　ethanol　and　n-butanol.　The　indicated　mean　effective　pressure　(IMEP)　was　distributed　in　a　wider　range　with　the　increase　in　λ　for　the　engine　fueled　with　ethanol　and　n-butanol.　However,　for　methanol,　the　IMEP　was　distributed　in　a　relatively　narrow　range　under　all　conditions　of　λ.　When　λ　was　increased　from　1.0　to　1.5,　the　coefficient　of　variation　in　IMEP　(COVIMEP)　of　methanol　increased　from　1.36%　to　2.65%,　the　COVIMEP　of　ethanol　increased　from　1.71%　to　10.46%,　and　the　COVIMEP　of　n-butanol　increased　from　2.06%　to　15.66%.　Thus,　methanol　had　a　higher　burning　rate,　lower　cycle-by-cycle　variations,　and　a　better　lean-burn　capability　than　that　of　ethanol　and　n-butanol.　©　2019　Elsevier　Ltd