It is important to know quantity of wash load for the integrated sediment management from upstream through downstream river basins. Generally, both continuous turbidity measuring and bottle sampling are used for suspended-sediment concentration measurement in rivers or reservoirs.<BR>Here, we have developed a new suspended sediment concentration measuring system with differential pressure transmitter (hereafter, we call SMDP). The SMDP has advantages in long-term and high turbidity measurement because differential pressure transmitter is measuring density of water directly. A floating type and a water circulating type are available, and both of them have shown good performances through field experiments at the Miwa dam, the Tenryu river and the Kurobe river.