Indoor　formaldehyde(HCHO)　pollution　is　harmful　to　human　health.　The　purpose　of　this　study　was　to　investigate　the　indoor　HCHO　situation　in　residential　apartments　in　Beijing　and　observe　the　character　of　the　concentrations.　According　to　Indoor　air　quality　standard　(GB/T　18883-2002),　HCHO　concentrations　in　decorated　apartments　were　investigated　during　2005-2007.　All　data　were　to　be　statistical　with　SPSS　16.0　for　Windows　software.　The　arithmetical　mean　(Mean)　was　0.15mg/m3　and　geometric　mean　(GM)　was　0.11mg/m3　in　our　study.　It　seemed　that　there　were　seasonal　variations　during　the　investigation,　and　the　highest　value　was　always　found　in　the　third　quarter　of　a　year　and　the　correlation　between　HCHO　and　temperature　was　more　significant　than　other　physical　factors.　It　should　be　taken　into　account　when　a　region　level　investigation　was　conducted.　©　2010　IEEE.