The invention provides a simulation experiment device and method for secondary crushing and fluidization of submarine gas hydrate. The simulation experiment device for the secondary crushing and fluidization comprises a secondary crushing pipeline, a rotating power assembly, a particle crushing knife tackle, a material falling assembly, a crushed particle recovery device and a control system, wherein the rotating power assembly comprises a motor and a rotating shaft, the particle crushing knife tackle is connected to the rotating shaft of the rotating power assembly through a flat key, the rotating power assembly is connected with a particle crushing pipeline through a bolt and a nut, the particle crushing pipeline is welded with a round-to-square flange plate and connected with the material falling assembly through a bolt and a nut, the crushed particle recovery device is placed on a crushing pipeline outlet, and the control system is connected with and controls the motor of the rotating power assembly and the material falling assembly. The crushing method adjusts the rotating speed of the rotating power assembly and the material falling speed of the material falling assembly through the control system, circulating water is pumped, non-premixed particles in a hopper is discharged down, and an outlet recovery device recovers crushed particles.