In　order　to　improve　the　accuracy　of　the　just　noticeable　difference　(JND)　model　in　transform　domain,　an　enhanced　JND　model　with　a　new　method　for　contrast　masking　factor　estimation　was　proposed.　The　image　was　decomposed　and　the　textural　image　was　used　for　an　accurate　block　classification,　thus　the　accurate　JND　in　DCT　domain　was　obtained.　The　improved　JND　model　was　applied　on　the　perceptual　image　coding.　Considering　the　compatibility　and　the　auxiliary　information　which　would　affect　the　encoding　efficiency,　the　JND　model　was　adjusted　to　the　quantization　process　and　removed　more　visual　redundancy.　Experimental　results　show　that　the　proposed　algorithm　can　improve　the　JND　threshold;　compared　with　JPEG　standard,　the　perceptual　coding　method　can　save　more　bit　rate　and　does　not　need　extra　bit　for　auxiliary　information　at　the　similar　visual　quality.　The　proposed　algorithm　is　also　applicable　to　the　perceptual　video　coding.