In　order　to　solve　the　residual　background　noise　resulted　by　the　existing　speech　enhancement　algorithm,　and　distorting　formant　of　speech　resulted　by　the　existing　loudness　compensation　algorithm　for　hearing　aids,　the　fusion　algorithm　based　on　speech　enhancement　and　loudness　compensation　for　digital　hearing　aids　is　proposed　in　this　paper.　According　to　human　auditory　perception　theory,　noisy　is　divided　into　several　sub-bands　by　Gammatone　filter　banks　simulated　the　cochlear　model　in　this　algorithm.　In　each　sub-band　denoising　and　loudness　compensation　are　achieved　by　multi-masking　and　sound　pressure　gain.　Experimental　results　show　that　the　background　noise　is　removed　effectively,　the　requirements　of　people　who　have　hearing　loss　of　sound　pressure　level　are　met,　and　formant　of　speech　get　well　protected.　Clinical　measures　show　that　the　intelligibility,　articulation　and　comfort　are　improved　for　hearing　losses　of　the　patients.