Different　InGaN/GaN　multi　quantum　wells　(MQWs)　structures　were　grown　by　metalorganic　chemical　vapor　deposition　(MOCVD).　Samples　were　investigated　by　photoluminescence　(PL),　atom　force　microscopy　(AFM)　and　double　crystal　X-ray　diffractometry　(DCXRD)　to　character　their　optical,　morphological　and　crystal　properties.　By　inserting　the　strain　relief　layer,　the　PL　intensity　was　increased　more　than　two　times.　The　surface　morphology　was　improved　and　the　density　of　V-pits　was　reduced　from　16-18　x　10(8)　to　6-7　x　10(8)/cm(2).　Further,　the　interface　abruptness　was　also　improved.　We　attributed　the　improvements　of　the　quality　of　InGaN/GaN　MQWs　to　the　relief　of　strain　in　the　InGaN/GaN　MQWs.　(c)　2005　Elsevier　B.V.　All　rights　reserved.