Abstract: Former workers used NTU values of an optical backscatter(OBS) to do sediment calibrations. Here we report the relation of counts values of OBS and suspended sediment concentration (SSC). The relation between OBS counts and SSC was established using laboratory calibration and in-situ calibration off old Yellow River mouth of Jiangsu Province. The relationship between OBS counts and SSC shows that OBS counts can be used to monitor the SSC. The results show strong linear relation between OBS counts and the SSC. The in-situ calibration can be used well in this area, while the laboratory calibration overestimates the SSC when it is used to calibrate in-situ data. And the difference of in-situ calibration between near shore sites and open sea site indicates that OBS observation is suitable for monitoring high SSC water.