Abstract: The experiments are conducted about the influence of the aeration on dynamic pressure on riverbed before the scour hole formed is formed.Results show that the aeration enlarges the dynamic pressure on the riverbed bottom in the jet impact field before the formation of the scour hole. However the dimensionless mean pressure distribution at jet stagnant,the dimensionless mean pressure distribution on riverbed and the dimensionless ultimate dynamic pressure distrbution of the non-aerated flow and the aerated flow obey same rules. The dynamic pressure on the scour hole bottom is studied by means of the experiments,and the dynamic pressure characteristic during the scour process in the jet impact field is obtained,which indicates that the influence of the aeration on the dynamic pressure on bottom of scour hole is not obvious,and the root mean square of dynamic pressure distribution of the aerated jet on the botom has no certain disciplinarian compared with the distribution of the non aerated pure water jet.