〔Abstract〕 Objective To explore the impact of pre-and post-set adaptive statistical iterative reconstruction Veo(ASiR-V) on imaging quality in the chest phantom. Methods The chest phantom had been scanned by GE revolution CT with the different weight of pre-set ASiR-V, which was set to 0%,20%,30%,40%,50%,60%,70%,80%,90%,and 100% successively. Then on the basis of pre-set ASiR-V set as 0%, 30% and 60%, images were reconstructed with post-set ASiR-V weight interval of 10%(from 0% to 100%) consecutively. A standard algorithm was used for original image reconstruction. The slice was 1.25 mm. The CT and SD value of various tissues at different level were recorded. Simultaneously, assessing subjective scores of lung and mediastinal windows under different proportions were evaluated to evaluate the discrepancy of image quality. Results With the increase of pre-ASiR-V weight, subjective scores of mediastinal and pulmonary window reached the best both at 30%. The subjective score of mediastinal window could ≥3 before 70%, while pulmonary window before 90%. There was no obvious change in the CT and SD values of various tissues. On the basic condition of pre-ASiR-V set to 0%, 30% and 60%, with the increase of post-ASiR-V, SD values of different tissues(except lung) showed a clear decreasing trend, while no significant difference was observed in CT values. The subjective scores of mediastinal and pulmonary window could meet the diagnostic requirements while post-set ASiR-V was no higher than 80% in the group of pre-set ASiR-V on 0% and 30%. The subjective scores of mediastinal and pulmonary window displayed fairly well and could meet the diagnostic requirement while post-set ASiR-V had been set on 60%～80% in the group of pre-set ASiR-V on 60%. Conclusion Excessive high pre-ASiR-V will generate the decline of image subjective scores. And excessive high or low post-ASiR-V weight will both do so. 60% pre-position combined with 60%～80% post-position ASiR-V is recommended for Chest CT scan while the default NI value is 14.