The invention discloses a visual model testing device and method for simulating water gushing in a tunnel. The device comprises a model test box, a water tank, a high-pressure water pump, a flow meter, a runoff flow and filling collecting device, a digital photographing non-contact measuring system, an osmotic pressure monitoring system, a fiber grating displacement monitoring system and the like. The testing device is characterized in that the catastrophe evolution process of water gushing in the tunnel is simulated, and anti-gushing rock mass crack growth and water gushing channel formation during water gushing can be directly observed. The device can quantitatively research water gushing behavior of the tunnel under different water pressure, different lithological characters and different thicknesses of anti-gushing rock masses, acquire coupling information of multiple fields such as stress fields, displacement fields, seepage fields and the like during water gushing of the tunnel, determine formation processes and forms of water gushing channels under the effect of different factors, disclose mechanical characteristics and evolution laws in anti-gushing rock mass structure progressive failure processes and provide an effective basis for the tunnel water gushing disaster incoming criterion and the minimum safe thickness analysis method.