The invention relates to the technical field of underground water pollution repairing, in particular to a simulating device of a zero-valent iron osmotic response grating. The technical problem of howto effectively monitor the reaction process of a zero-valent iron osmotic response grating is solved. The simulating device comprises a water supply mechanism for preparing an underground water solution and a reaction column vertically fixed to a support. A weighing unit is arranged on the lower side of the support. The reaction column is filled with a zero-valent iron medium. The bottom end of the reaction column is provided with a first water inlet, and the top end of the reaction column is provided with a first water outlet. The first water inlet is connected with the water supply mechanism. The first water outlet is connected with a gas collector and a waste liquid bottle. On the basis of the structure, the working process of the permeation reaction grating can be simulated, the yieldof hydrogen and precipitates in the zero-valent iron reaction process is effectively monitored and precisely measured, the performance of the zero-valent permeation reaction grating can be conveniently predicted by technicians, and the data support is provided for designers to improve the design of the zero-valent permeation reaction grating.