The　spray　characteristics　of　the　pressure　swirl　nozzle　are　experimentally　studied　using　particle　dynamics　analysis　(PDA)　and　high-speed　photography　system　in　this　paper,　specifically　focusing　on　the　dependence　of　geometrical　dimensions　of　orifice　on　the　spray　SMD,　velocity　magnitude　and　droplet　distribution,　and　the　spray　cone　angle.　It　is　indicated　that　the　increase　of　orifice　diameter　makes　the　initial　swirling　velocity　lower　and　the　spray　liquid　film　thicker.　When　the　spray　cone　is　fully　expanded,　the　flow　rate　of　900　mu　m　orifice　diameter　nozzle　increases　by　30-40%　and　the　SMD　of　900　mu　m　orifice　diameter　nozzle　increases　by　8.5%　compared　with　that　of　700　mu　m　orifice　diameter　nozzle.　According　to　the　experimental　conditions,　the　relationship　between　Re　and　spray　angle　was　calculated　as　theta　=　29.97*Re-0.087,　ignoring　the　factors　that　had　little　influence　on　spray　angle.　The　decrease　of　the　orifice　length　makes　the　distance　of　gas-medium　shearing　action　shorten　so　that　thinner　oil　film　near　wall　cannot　be　formed　by　the　extrusion　of　air　core,　leading　to　the　swirling　intensity　reducing　and　the　suction　effect　weakened.　The　spray　cone　angle　of　the　450　mu　m　orifice　length　atomizer　is　about　5　degrees　smaller　than　the　nozzle　of　500　mu　m　orifice　length,　and　more　small　SMD　droplets　are　not　sucked,　resulting　in　the　distribution　range　of　spray　SMD　declining.