With　the　development　of　numerically　control　and　digital　drive,　it　is　a　trend　to　put　the　Electronic　Line-Shaft　(ELS)　technology　into　printing　machine　instead　of　the　Mechanical　Line-Shafting　(MLS).　After　the　shaftless　reform　of　a　printing　machine　for　a　factory,　it　was　found　that　the　printing　accuracy　and　speed　of　most　printing　units　was　improved　observably　except　the　folding　ripple.　The　paper　analyzes　the　formation　reason　of　folding　ripple　and　the　different　characteristics　between　ELS　and　MLS.　The　research　result　shows　that　also　there　are　many　advantages　in　using　ELS　the　synchronous　capability　is　less　than　MLS　when　a　periodic　disturbance　act　on　them　under　the　same　transmission　stiffness.　Therefore　it　is　proposed　that　the　AC　motors　must　connect　directly　to　the　main　printing　roller　to　decrease　the　periodic　disturbance　and　to　increase　the　stiffness　during　the　shaftless　reform　of　printing　machine.