A remote sensing technique has been developed for quickly detecting suspended sediment concentration and monitoring the transport and deposition of suspended sediment in a large estuary area4. There is an agreement that the best wave band to analyse suspended sediment concentration is 0-6-0-8μm (MSS 5 and TM 3 for Landsat), but it is suggested that there is a divergence between which model is used to study the suspended sediment best. This paper presents a unified model for a quantitative approach to suspended sediment concentration using remote sensing. The comparison between various models with field investigation data and published data has shown that the unified model has a higher correlation and precision than most popular models used currently. The author illustrates that the logarithm model is flawed when suspended sediment concentration is high. The unified model has been applied to the quantitative remote sensing of suspended sediment in Lingdingyang, the Pearl River estuary (the biggest river in South China). Further improvement to the unified model with TM3/TM5 ratio technique has also been proposed to minimize the background influences (atmospheric and solar effects). Results show that the improved unified model has more advantages than other models which usually need a large number of field data each time they are used. The improved united model can be applied to a global scale after its parameters are classified according to different regions.