In　order　to　establish　a　numerical　analysis　method　for　fatigue　crack　initiation　and　short　crack　propagation　in　polycrystalline　steels,　a　microstructure　model　with　cumulative　fatigue　damage　was　generated　based　on　Roe-Siegmund　cyclic　cohesive　zone　model　and　Voronoi　diagram　method,　and　the　mechanical　properties　of　grains　at　the　microscopic　level　were　considered.　Each　grain　was　assigned　a　random　local　coordinate　system　and　an　anisotropic　linear　elastic　constitutive.　Finally,　the　effects　of　the　microscopic　defects　such　as　pores　and　inclusions　on　the　crack　initiation　path　and　life　were　studied.　The　results　show　that　the　method　is　consistent　with　the　actual　situation　in　the　crack　initiation　path,　and　there　are　two　fracture　modes,　transgranular　and　intergranular,　with　the　latter　being　the　dominant　one.　The　crack　initiation　life　range　values　in　accordance　with　the　normal　distribution　can　be　obtained,　which　is　consistent　with　the　experimental　in　the　literature.　The　crack　initiation　path　and　the　life　of　the　crack　initiation　are　changed.　©　2025　Editorial　Board　of　Mechanical　Science　and　Technology　for　Aerospace　Engineering.　All　rights　reserved.