MWCNTs/poly　(pyrrolyl　methine)　composites　with　the　different　contents　of　MWCNTs　were　synthesized　by　in-situ　ultrasonic　polymerization,　and　their　structures　and　photophysical　properties　were　also　investigated.　The　results　revealed　that　the　third-order　nonlinear　optical　susceptibility　of　MWCNTs/PHPDTBE　composite　showed　a　rapid　increase　with　the　increase　of　MWCNTs’　content,　and　obtained　a　maximum　value　of　3.41 × 10−7　esu,　which　was　almost　ten　times　larger　than　that　of　PHPDTBE　of　3.49 × 10−8　esu.　The　enhanced　optical　nonlinearity　was　attributed　to　strong　photoinduced　electron　transfer　from　PHPDTBE　to　MWCNTs　by　right　of　their　strong　noncovalent　π-π　interaction　in　the　photoexcited　state.　©　2016　Elsevier　B.V.