Abstract: We use Klobuchar model and Dual-frequency observation model to calculate TEC values with the data provided by IGS center over low-latitude and mid-latitude areas in ionospheric quiet period and active period. Then improve 7th day's TEC values calculate by Klobuchar model with the difference values come from the forecast difference values in each epoch of the preceeding 6 days between Klobuchar model and Dual-frequency observation model by the Holt exponential smoothing model. The experiment results show that the correction effect of improved model has a significant improvement than the basic model no matter whether it is in in ionospheric quiet period or active period. In addition, the improved model can better reflect the ionospheric changing characteristics, especially the night ionospheric changing characteristics.