Considering　that　an　irregular　ubiquitiformal　fracture　surface　is　resulted　from　the　heterogeneity　of　rock　material,　a　numerical　simulation　on　the　extension　of　a　ubiquitiformal　crack　in　rock　material　was　carried　out　by　using　the　ABAQUS　software,　together　with　the　Weibull　distribution　characterization　of　the　heterogeneity　of　material　properties.　The　ubiquitiformal　crack　extension　of　rock　material　under　dynamic　tensile　loading　was　analysed　and　the　complexity　of　the　fractured　profile　was　calculated　by　using　the　box　counting　dimension.　The　numerical　results　were　in　good　agreement　with　previous　experimental　data.　The　results　of　the　crack　extension　path　and　the　complexity　of　the　fracture　surface　under　different　strain　rate　show　that　the　complexity　decreases　with　the　increase　of　strain　rate.　Furthermore,　from　the　analysis　of　ubiquitiformal　fracture　energy,　it　is　found　that　the　energy　release　rate　increases　with　the　increase　of　strain　rate.　Under　lower　strain　rate,　the　crack　propagates　in　the　direction　of　minimum　energy　dissipation,　while,　with　the　increase　of　strain　rate,　the　crack　penetrates　through　the　higher　fracture　energy　element　and　propagates　along　the　self-similar　extension　direction.　These　results　imply　that　the　strain　rate　effect　on　the　extension　of　the　ubiquitiformal　crack　can　be　induced　by　the　heterogeneity　of　rock　material,　which　could　help　to　understand　the　mechanism　of　ubiquitiformal　fracture.　©　2018,　Editorial　Office　of　Journal　of　Vibration　and　Shock.　All　right　reserved.