Abstract: The interior construction and performance of four photocatalytic air purifiers were tested and analyzed detailedly, which was bought from domestic and abroad market. Testing experiments were conducted in a 4 cubic meter airproof chamber using the formaldehyde analyzer which 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 method and interior construction design. The performance of four photocatalytic air purifiers was estimated objectively by means of the index of clean air delivery rate and the time needed to decompose 90% of the air contaminants.