With　the　rapid　progress　of　urbanization,　urban　agglomeration　has　become　an　important　distribution　form　of　regional　space.　The　eastern　coastal　region　of　China　has　the　highest　level　of　urbanization　and　the　most　developed　economy　in　the　country.　The　Beijing-Tianjin-Tangshan　area,　the　Yangtze　River　Delta　and　the　Pearl　River　Delta　are　three　major　urban　agglomerations　in　this　region.　In　this　paper,　urban　heat　island　changes　and　their　relationships　to　the　urbanization　of　these　three　major　urban　agglomerations　from　2001　to　2013　were　analyzed　using　MODIS　land　surface　temperature　(LST)　and　DMSP/OLS　night-light　data.　The　results　show　that　during　the　12-year　study　period　the　heat　island　patches　in　these　three　urban　agglomerations　have　sprawled　to　a　large　extent　and　gradually　connected　to　form　the　heat　island　zones.　The　Regional-Heat-Island　Index　(RHII)　in　these　three　urban　agglomerations　has　been　increasing,　which　demonstrates　that　the　urban　heat　island　effects　are　aggravating.　The　RHII　in　the　Beijing-Tianjin-Tangshan　area　increased　by　0.051,　from　0.524　in　2001　to　0.575　in　2013,　in　the　Yangtze　River　Delta　the　RHII　increased　by　0.070,　from　0.491　to　0.561　and　the　RHII　in　the　Pearl　River　Delta　increased　by　0.101,　from　0.441　to　0.542.　We　also　found　that　the　radiation　effects　from　the　urban　areas　on　their　surrounding　areas　have　been　strengthening.　Furthermore,　night-light　brightness　and　LST　in　suburban　areas　have　increased　more　than　those　in　built-up　areas.　There　is　a　close　relationship　between　night-light　and　LST　in　spatial　distribution.　On　the　whole,　the　expansions　of　urban　agglomerations　have　induced　the　strong　regional　heat　island　effect.　The　regression　analysis　shows　that　the　relationship　between　urban　heat　island　and　urban　development　is　a　logarithmic　one.　©　2018,　Editorial　Board,　Research　of　Environmental　Sciences.　All　right　reserved.