The invention provides riverway water quality purification and ecosystem restoration adjustable wetland technology, which comprises that: a rubber dam with adjustable height is arranged in a riverway;potamogeton plants are planted at the upstream of the rubber dam of the riverway to form artificial wetland; the planting density of the potamogeton plants is between 20 and 30 clusters/m<2>, and a cluster is between 3 and 4 plants; the retention and purification time of river water in the artificial wetland is adjusted by adjusting the height of the rubber dam, the height of the rubber dam is improved in normal and dry seasons to store water to make the water level at the upstream of the rubber dam of the riverway improved, and the adjusting height of the rubber dam is determined by the CODconcentration of the river water at the inlet of the artificial wetland and the temperature of the river water. By planting the potamogeton plants in the riverway to form the wetland, instead of lifting the water onto land to construct an artificial wetland, the technology can more directly and effectively restore the damaged riverway ecosystem, improve the water quality of polluted river water, and can ensure normal flood discharge of the riverway in flood season.