The utility model discloses an effectively monitor device that subsides on river island, including the river island of arranging a monitoring structure and the land of arranging the 2nd monitoring structure, the river island is right at a distance from the river facies with land, and a monitoring structure includes: the ground on river island is inserted to one end, first stake that the other end surfaced and installed a laser range finder, and a laser range finder is connected with a wireless transmitter, the 2nd monitoring structure includes: terrestrial ground is inserted to one end, and the other end lies in the second stake that the 2nd laser range finder was just installed in surface of water top, and the 2nd laser range finder is connected with the 2nd wireless transmitter, the utility model discloses a laser range finder measures river island and the distance of land apart from the surface of water to with distance display on the display, whether audio -visual control river island is subsided, when river island and land were the definite value apart from the range difference of the surface of water in addition, then the river island was not subsided.