Abstract: Based on the 218 flood events data of the lower Yellow River from 1950 to 1985,different channel transverse adjustment at Huayuankou reaches of the lower Yellow River at rising and falling stages during flood events are distinguished.At the rising stage,the width to depth ratio at Huayuankou reaches exhibits the tendency of generally increasing.The higher the maximum sediment concentration of the flood events,the larger the width to depth ratio.When the flood peak-increasing ratio is lower than 3,the width to depth ratio is in direct rat io to it.When it is higher than 3,the width to depth ratio is in inverse ratio to it.At the falling stage,the situation is just on the contrary When the maximum sediment concentration of the flood events is lower than 15 kg/m³ or higher than 300 kg/m³,the width to depth ratio is in net decrease.When the flood peak-increasing ratio is higher than 3,the width to depth ratio of the most flood events will decrease.The deformation of the channel during flood events is firmly related to sediment concentration.When the sediment concentration of the flood events is low,the decrease of the width to depth rat io is mainly at rising stage.When the sediment concentration of the flood events is high,the decrease of the width to depth ratio is mainly at falling stage.