Based on the chart of year 1972 to 2007 and hydrological data of mouth bar around the Karsimu port Ahsan channel,we probe into the mouth bar evolution characteristics and its influence on Ahsan channel.The results show that the Ahsan channel and mouth bar are relatively stable in the 1970 s,but in the 1990 s,with the increase of the human factors,and under the influence of natural conditions,the Ahsan channel axis changed.Recently,the scour rate around channel increased,the water around waterway became shallow,deposition turned more serious and the channel maintenance work increased.