The　interior　construction　and　performance　of　four　photocatalytic　air　purifiers　were　tested　and　analyzed　in　detail,　which　was　bought　from　domestic　and　abroad　markets.　Testing　experiments　were　conducted　in　a　4　cubic　meter　airproof　chamber　using　the　formaldehyde　analyzer　which　was　produced　by　America　InterScan　Company.　The　performance　of　each　composing　element　inside　different　air　purifiers　was　analyzed　systematically.　The　results　show　that　those　photocatalytic　air　purifiers　have　many　lacks　in　performance　due　to　different　photo-catalyst-loaded　methods　and　interior　construction　designs.　The　performances　of　four　photocatalytic　air　purifiers　were　estimated　objectively　by　means　of　the　index　of　clean　air　delivery　rate　and　the　time　needed　to　decompose　90%　of　the　air　contaminants.