Hydrogen-assisted　diesel　injection　is　suitable　for　low-power　and　high-power-to-weight　ratio　in-cylinder　piston　direct　injection　engines.　The　jet　characteristics　of　hydrogen-assisted　diesel　direct　injection　have　an　important　effect　on　engine　performance.　The　effects　of　fuel　injection　duration　and　mixture　duration,　hydrogen　pressure　and　fuel/hydrogen　premix　time　on　spray　penetration　distance　and　diffusion　area　were　qualitatively　analyzed　by　high-speed　photography　on　a　constant　volume　chamber　test　bench.　The　results　show　that　increasing　the　fuel　injection　duration　increases　the　penetration　distance　and　decreases　the　spray　projection　area.　Increasing　hydrogen　pressure　will　increase　both　penetration　distance　and　spray　projection　area.　Increasing　the　duration　of　air　injection　will　increase　the　penetration　distance　and　decrease　the　spray　area.　The　spray　area　increases　with　the　increase　of　fuel/hydrogen　premixing　time,　and　tends　to　be　stable　when　the　premixing　time　is　3ms,　which　has　no　effect　on　the　spray　penetration　distance.　©　2022　Proceedings　of　WHEC　2022　-　23rd　World　Hydrogen　Energy　Conference:　Bridging　Continents　by　H2.　All　rights　reserved.