In this paper, the building prare of the auroral electrojet was analytal and it was consided that there is a posihve feedback, therefore a transient process during the building pedod' To probe the physics mecanism, a simple model was utal in this paper to sdriulate the building of the auroral electrojet. The results show that there does be a transient process in the auroral electrojet. The structure along the eleCtrojet of curmt, net charge or conductivity is a propagahng jump, whereas the elecric field kaps neariy invariable.The calculatal results agree to the observahons rather well.