The invention relates to an internal carbon source-oxygen enrichment stair combination constructed wetland engineering reactor. The reactor is of a three-level tandem connection type and sequentially comprises a first-level surface flow artificial wetland (1), a second-level vertical underflow artificial wetland (5) and a third-level denitrification horizontal underflow artificial wetland (12), wherein a middle seperation guide wall (18) is arranged among the levels; and an impermeable layer (2) is arranged at the bottom layer of each level. The internal carbon source-oxygen enrichment stair combination constructed wetland engineering reactor is capable of effectively realizing the grading removal of organic matters and ammonia nitrogen in printing and dyeing wastewater, overcoming the shortcoming that aerobic degradation of the organic matters, nitration and denitrification are difficult to realize at the same time by using one traditional constructed wetland unit and increasing the running effect of a conventional water treatment technology and the safety of water, and has good application prospect.