The utility model discloses a gas mixing device and an oxygen-enriched combustion boiler. The gas mixing device comprises a pipeline (1) and a plurality of mixing stations (2), the pipeline (1) is used for allowing gas to pass, the mixing stations (2) are arranged in the extending direction of the pipeline at intervals, a plurality of gas injection devices (3) are arranged at the position, on each mixing station, of the pipeline around the pipeline, the gas injection devices are obliquely arranged in the same rotating direction of the pipeline towards the same side relative to the positions, on all mounting areas, of the surface of the pipeline or the plane tangent to the surface of the pipeline so that preset included angles can be formed between the injection directions of all the gas injection devices and the positions, on all the mounting areas, of the surface of the pipeline or the plane tangent to the surface of the pipeline, the preset included angles are not equal to 90 degrees, and the injection directions of the gas injection devices on the adjacent mixing stations are different. The gas mixing device has high safety and the good mixing effect.