The invention provides a net device for trapping lepturichthys fimbriata in rivers and lakes. The net comprises a net device frame formed by welding rebar stand columns mutually. The outer side surface of the net device frame is wrapped in net piece walls so that a rectangular net device body is formed. The two ends of the net device body are provided with fish inlets. The net piece walls on the inner sides of the fish inlets are connected with opening fixing frames inward in an inward-concave and extending manner. The opening fixing frames are provided with tapered steel bars which are fixed through the opening fixing frames and the net piece walls. The net frame covered with the net piece walls are provided with two fish fetching bag fish inlets and two fish fetching bags at the middle portions of the two sides of the net body. Upper and lower net ropes are used for connection and fixation of the two fish fetching bags and steel bar supporting rings support the inner space thereof up to fish fetching opening tying ropes. The two fish fetching bag fish inlets are each connected with a fish inlet inner tapered unit. The two fish inlet inner tapered units extend inward and are connected with inner tapering openings. Inner tapering opening pull ropes are used for connection and fixation of the two inner tapering openings.