Abstract: As a world famous spectacular scene of tidal bore of Qiantang estuary,at present it becomes a special focused problem that the height of the tidal bore decreases or increases after the large-scale regulation and reclamation on Qiantang estuany.Based on the data of the height of tidal bore measured on the spot before and after the action on Qiantang estuary,it shows that,during the strong tide,the reach of highest tidal bore is transformed from Xinwan to Daquekou and increases by 0.4 m after the action than before that of the reaches under Yanguan,and the reach in Yanguan increases by 0.1 m,while the variation on height of the tidal bore of the reachesup Yanguan is closely related with the status of the sandbank peak rushed and silted by runoff.It also shows the height of tidal bore increases under the same other conditions.The result conforms to the fact that the standard swawall overflows take place due to the height increment of the tidal bore after the regulation and reclamation in recent years.