HIV-1　integrase　catalyzes　the　integration　of　virus　DNA　into　the　host　chromosome,　which　is　a　crucial　step　in　viral　replication.　The　inhibition　of　integrase　activity　is　an　effective　measure　to　prevent　HIV-1　replication.　Moreover,　integrase　has　no　known　functional　analogue　in　human　cells.　Therefore,　integrase　becomes　an　ideal　target　for　anti-HIV　therapy.　During　the　past　decade,　in　vitro　assays　have　been　developed　and　applied　to　monitor　the　enzymatic　activity　of　the　integrase,　study　the　reaction　mechanisms　of　integase　and　screen　integrase　inhibitors　in　vitro.　This　review　describes　the　recent　development　on　integrase　activity　assays.