The invention relates to a water quality detection device, in particular to a lake water quality detection and sampling device for water conservancy. The invention aims at providing a lake water quality detection and sampling device which can collect the water at different positions and at different depths, can alleviate the labor intensity and can improve the safety. The lake water quality detection and sampling device for the water conservancy is characterized by being comprising a bottom plate, an installation block, a first rotating shaft, a supporting plate, a placement plate, a collection box, a connecting plate, a water collection box, a sealing ring, a baffle plate, an installation box, a wireless control module and a power supply; and the upper-middle portion of the bottom plate is connected with the installation block, and the front side of the installation block is connected with a first rotating shaft in a rotating manner. The water collection box is submerged in the waterdue to the balancing weight, so that the water at different positions and at different depths in a lake can be sampled, the water in the lake does not need to be manually sampled by virtue of a boat,the labor intensity can be alleviated, and the safety can be improved.