Underwater　image　enhancement　is　an　important　low-level　task　for　marine　industry.　This　paper　proposed　an　underwater　image　enhancement　method　based　on　colour　constancy　theory.　Compared　with　many　existing　researches,　time　and　space　complexity　of　the　method　proposed　in　this　paper　is　low　and　our　method　achieves　excellent　performance.　Firstly,　we　analyzed　the　underwater　imaging　model　and　distortion　of　underwater　images.　Then,　by　compensating　the　specific　channel　and　local　white　balance,　the　linear　transformation　is　performed　on　the　images　to　restore　distortion　in　the　images.　Finally,　the　results　are　obtained　by　stretching　the　histogram　on　RGB　channel　and　intensity　channel　of　images.　Experiments　show　that　our　method　has　achieved　excellent　performance.