The invention relates to a turning double-piston annular multi-cylinder internal combustion engine capable of directly using hydrogen and oxygen as a fuel. The out sides of the middle rings of two pistons are both fixedly provided with piston blades, the number of which is equal to the number of cylinders on a shell, and under the control of a plurality of controllers in a shell control inner ring, the two pistons alternately and oppositely rotates in the outer cylinders of the shell, the two layers of tooth processes distributed on an output gear set can be respectively meshed with the innerring gears of the two pistons, and the two pistons drive the output gear set to rotate and output mechanical energy outwards through a gear meshing mode. A work cycle of the piston comprises four processes, process one and process three are similar, and the alternating of work and standstill of the two pistons is finished, process two and process four are similar, and all the processes are the process of working and producing energy. The whole work cycle does not have a compression process, and gas exhaust is synchronized with the working, two pistons do not perform reciprocating motion and acrankshaft is not needed, and hydrogen and oxygen can be directly combusted.