As　pavement　crack　images　are　difficult　to　segment　due　to　the　existence　of　high　noise,　weak　boundary　and　small　cracks,　an　extraction　method　of　pavement　cracks　based　on　the　valley　edge　detection　of　fractional　integral　is　proposed.　In　this　method,　first,　neighboring　smoothing　of　the　original　image　is　performed　to　eliminate　the　noise　and　expand　the　relative　width　of　the　cracks.　Then,　the　main　cracks　are　extracted　via　the　valley　edge　detection　of　fractional　integral,　and　the　resulting　image　is　further　processed　via　the　morphological　approach　with　short-line　noise　elimination.　Afterwards,　final　cracks　are　extracted　by　using　the　gap　linking　method　on　maximum　entropy　threshold　to　cause　cracks　to　merge　automatically.　Experimental　results　show　that　the　proposed　method　instantly　helps　to　detect　small　pavement　cracks　with　high　accuracy　and　strong　noise　robustness.