Abstract: In order to improve aerodynamic deceleration efficiency, deep space reentry capsules generally adopt large blunt windward shape and ablative heat protection system. However, factors such as the flat forebody shape and the sharp increase in surface roughness caused by aerothermodynamic heating and ablation easily lead to the instability of the windward flowfield of the capsule, resulting in the transition or even evolution into turbulence, which greatly changes the distribution of the surface heat flux and brings great challenges to the safety of the capsule. Formerly the studies on the instability mechanism and simulation for the transition of hypersonic boundary layer under the change of microscopic morphology of large blunt heat shield are relatively unexplored. Using the γ-Re_θ transition model and k-ω-γtransition model based on hypersonic and rough element correction, the intermittent factors of rough element equivalent roughness height, incoming Reynolds number, angle of attack and chemical non-equilibrium basic flow on the windward surface of the large blunt heat shield were analyzed. The development law of hypersonic boundary layer transition and aerothermodynamic effect on ablative rough surfaces of deep space reentry capsules were studied.