The invention provides an automatic monitor for suspended load sediments in river water. The automatic monitor comprises a sample container with a water inlet, an overflow port and a water outlet, a weighing instrument which is electrically connected with a controller, a water pump which is electrically connected with the controller, and the controller, wherein a solenoid valve is arranged on the water outlet; an inlet of the water pump is connected with one end of a water inlet pipe, and the other end of the water inlet pipe stretches into water to be monitored; an outlet of the water pump is communicated with the water inlet of the sample container; the controller is used for transmitting instructions to the water pump, the weighing instrument and the solenoid valve respectively according to preset starting conditions and controlling actions of the water pump, the weighing instrument and the solenoid valve. The water pump is controlled to pump water in a specified volume into the sample container at a specified time point through the controller, the sample container containing water is weighed by the weighing instrument, and finally, the controller can obtain the content of suspended load sediments in water according to weighing data, the volume of pumped water and the specific gravity of the suspended load sediment. Moreover, monitoring conditions are input into the controller in advance, and manual sampling and other processes are not required, so that the monitoring efficiency is improved, and manual labor is reduced.