The invention discloses a hydrogen-oxygen cutting robot inside a steel pipe, which comprises a central axis, a linear slider, wheels, a hydraulic cylinder, a cutting frame, an electrode, an electrolytic cell, an air guide pipe joint, and a cutting tube, and a linear slider is slidably installed on the central axis. A third link bracket is fixedly installed on the linear slider, a third link is hingedly installed on the third link bracket, a first central shaft seat is fixedly installed on the central shaft, and a first central shaft seat is fixedly installed on the first central shaft seat. The link bracket, the first link bracket is hingedly installed with the first link, the other end of the first link is hingedly installed on the first link seat of the support plate, and the first link seat of the support plate is fixedly installed on the support plate, The rotating motor gear meshes with the rotating airway gear. The invention is easy to use, can complete the cutting of the steel pipe from the inside of the steel pipe, has good cutting effect, and can complete some cutting work that cannot be completed outside the steel pipe.