In this paper, basic theory and key technology of tr ansient laser holographic interferometry are described. Some experimental result s are given. Recent research and developed instruments for holographic interfero metry are introduced. The four parts in this paper are following: 1) describing the physical process and mathematical model on off-axis holography;and 2) key technology of transient holographic interferometry;3) introducing typical equip ments for measurement;4) discussing several problems.