The Nahshon-Hutchinson shear modified GTN damage model was used to simulate the mechanical and damage behavior of small punch test（ SPT）,where the study material is silicon steel. Based on finite element simulation and factorial experimental design method,the influence degree of the damage evolution parameters on the SPT load-displacement curve were evaluated,and three key impact damage evolution parameters（ f,N,ε,N,k,s,） were identified,the response surface method（ RSM）was then used to determinate the three key damage parameters. The facture parameters（ fc,fF） was determined by comparing the SPT load-displacement curve obtained by simulation and experimental results. Finally the effective of the identified parameters were verified by SPT experiments with different specimen thickness.