In the past thirty years, the coastwise change has been very obvious in the lower reaches of the

Beijiang River. With the development of economy, the riverway environment has changed tempestuously, but the mastery

of the change regularity is very difficult on the basis of traditional measures. With the advantages of macroscopic,

dynamic and systematic researches, the RS technology can be used to study the characteristics of riverway evolution

form the view of spanning a historical period of time. Using MSS and TM as the data source including 7 periods in

the past thirty years and the 1︰50000 topographic map, the authors studied the flux of the riverside, the evolution

of the bottomland and riverway by using 3S and on the basis of RS recognition symbols and characteristics of the

image. According to the 3S analysis of the data available between 1975 and 2002, the riverway experienced an obvious

evolutionary process, the bank and bottomland changed distinctly, and part of the area was filled up. According to

the characteristics of the transverse evolution of the riverway relative to the longitudinal evolution in this

period，it is concluded that the longitudinal distortion of the riverway affected the transverse distortion, i.e.,

there exists an inverse variation relationship between the transverse distortion and the longitudinal distortion.

The development trend of the riverway seems to become increasingly steady.