The　flow,　breakup　and　atomization　characteristics　of　conical　liquid　film　under　different　injection　pressures　in　a　swirl　nozzle　are　investigated　with　particle　dynamic　analyzer(PDA)　and　high-speed　photographic　system　in　this　study.　The　effect　of　the　liquid　film＇s　velocity　on　its　breakup　and　variation　rule　of　spray　quality　parameters　was　analyzed　under　different　injection　pressure.　The　dispersion　equation　of　the　conical　liquid　film　was　solved　by　combining　the　corresponding　experimental　data,　which　verified　the　influence　of　the　injection　pressure　on　the　breakup　of　liquid　film.　The　increasing　injection　pressure　will　increase　the　nozzle　flow　rate　and　the　droplet　flow　velocity,　reduce　the　liquid　film　breakup　length　and　the　SMD(average　diameter　of　Salter)　in　the　spray　field,　the　tangential　velocity　of　liquid　film　has　obvious　effect　on　conical　liquid　film　and　make　the　spray　angle　firstly　increasing　and　then　stable.　Under　the　same　injection　pressure,　the　film　velocity,　the　droplet　velocity,　as　well　as　the　spray　field　concentration　and　uniformity　are　higher　for　the　nozzle　with　larger　swirl　slot　number,　while　the　spray　cone　angle　is　smaller.　The　growth　rate　of　liquid　film　surface　waves　was　obtained　by　solving　the　dispersion　equation,　which　proves　that　the　increase　of　the　swirl　slot　number　raises　the　growth　rate　of　liquid　film　surface　waves,　and　finally　decreases　the　breakup　length　of　liquid　film.　©　2021　Journal　of　Mechanical　Engineering.