The invention provides a water injection and drainage system of large tunnel simulation loading equipment. The water injection and drainage system includes a spliced structure, an embedded loading structure and a water injection device; the spliced structure is a sealed frame which is obtained by splicing an upper top plate, a front wall, a rear wall, a left side plate, a right side plate and a base, wherein the base is provided with a water drainage opening; the embedded loading structure includes a hydraulic cylinder, a push rod and a push plate; the embedded loading structure is embedded into the upper top plate, the left side plate and the right side plate of the spliced structure; a sealing bar is arranged at the push rod, so that sealing can be completed; the water injection device is arranged in the spliced structure; and the water injection device includes horizontal pipes and vertical pipes; the cavities of the vertical pipes are communicated with the cavities of the horizontal pipes; the horizontal pipes are provided with water injection openings; each vertical pipe is provided with a plurality of water outlets; and one or a plurality of water injection devices are adopted. The system has good sealing performance and can rapidly inject water into compacted soil. After an experiment is completed, the push plate is controlled to squeeze the soil, so that water drainage speed can be increased, and therefore, the efficiency of the experiment can be improved.