Abstract: The rebar corrosion process is newly partitioned in this paper.Based on the concept of corrosion parameters and principle of deformation harmony,the relation among the parameters of δ,δ′,η₀,n,P_K and d₀,is deduced,and which are respectively represented iron rust filling zone,increment of corrosion rebar diameter,critical rustiness rate,coefficient of rust expansion,opening voids within concrete and steel initial diameter.A model of calculating rust filling zone relative value δ/d₀ on a free expansion stage is built up,and a theoretical model of calculating main pressure stress value q^* due to rust expansion on expansion force formation stage is also set up according to mass conservation law.It is verified to be reliable and suitable for the calculation models by indoor test result analysis and also proved to be correct by the corrosion expansion ANSYS simulation trial.The models is useful for forecasting service life of concrete.