Abstract: For using enclosed-gate layout MOSFETs in rad-hard by design,because the annular structure is different from ordinary rectangular gate essentially,so the conventional SPICE simulations is not-applicable to radiation-hardening design.In this paper,analyzing the characteristic of enclosed-gate in deep submicron technology,this thesis establishs s an effective aspect ratio arithmetic and buildes SPICE model for enclosed-gate,at the same time,a method about how to extract layout netlist availability is presented here,the three points mentioned above expound the simulation method of radiation-hardening design in deep submicron technology,which resolved the unapplicability between SPICE and RHBD traditionally.Throuth effective simulation,the circuit performance is ensured and reliability in the design is increased.