Since　the　invention　of　lasers　in　the　1960s,　the　pulse　duration　has　being　continuously　shorten　down　to　the　sub-picosecond　and　even　femtosecond　regime.　It　makes　the　laser　processing　technology　to　the　ultrashort　pulse　laser　era.　In　order　to　further　optimize　the　ultrashort　pulse　laser　micro-machining,　theoretical　study　is　indispensable.　The　interaction　mechanism　between　ultrashort　pulse　laser　and　different　types　of　materials　were　presented.　The　typical　physical　properties,　such　as　plasma　effect,　self-focusing　and　filamentation,　and　conical　radiation,　were　discussed.　The　theoretical　studies　for　ultrashort　pulse　laser　drilling　of　micro-hole　were　analyzed.　Furthermore,　the　challenging　issues　were　obtained.　©　2019,　Editorial　Board　of　Journal　of　Infrared　and　Laser　Engineering.　All　right　reserved.