The invention discloses a visual testing device and method for simulating the forming condition of bottom water coning of a vertical well and a horizontal well of a bottom water gas reservoir. The visual testing device comprises a water cone model, a stratum water intermediate container, a natural gas intermediate container and a high-pressure displacement pump. The water cone model comprises a water cone model shell. The water cone model shell is provided with a sand filling hole and a sand filling hole cover, is internally provided with a simulative well and is provided with an observation window. The bottom of the water cone model shell is provided with a sample inlet, and the top of the water cone model shell is provided with a top outlet communicating with a well mouth of the simulative well. An outlet of the high-pressure displacement pump is connected with the inlet pressure end of the stratum water intermediate container and the inlet pressure end of the natural gas intermediate container. An outlet of the stratum water intermediate container and an outlet of the natural gas intermediate container are connected with the sample inlet through pipelines. The top outlet is connected with a gas-liquid separating device through a back-pressure valve. A gas outlet of the gas-liquid separating device is connected to a gas meter. The visual testing device and method can simulate the forming condition of bottom water coning of the vertical well and the horizontal well of the bottom water gas reservoir and are used for guiding reasonable and efficient mining of the bottom water gas reservoir.