The invention discloses a combustion cavity for an integral fuel oil ejecting radial hydrocyclone with functions of premixing, pre-evaporation and low pollution. The combustion cavity has a single ring cavity structure, and consists of a combustion cavity head and a flame tube, wherein the combustion cavity head comprises a precombustion stage positioned at the center and a main combustion stage positioned at the peripheral. The main combustion stage comprises a direct jet type air atomizer spray nozzle and a main combustion stage radial hydrocyclone. The jetting of the main combustion stage fuel oil and the main combustion stage radial hydrocyclone are integrated. The main combustion stage fuel oil ejected by the direct jet type air atomizer spray nozzle enters into a main combustion stage radial hydrocyclone vane channel of a main combustion stage radial hydrocyclone vane, and the fuel oil is mixed with the rotary flow air of the main combustion stage radial hydrocyclone. A premixedoil-gas mixture enters into a combustion zone through a main combustion stage mixing cavity to be combusted. The combustion mode can effectively reduce pollutant emission in the combustion cavity andreduce the length of the combustion cavity. The combustion cavity is mainly used for an aerial engine combustion cavity, and also can be used for the combustion cavities of industrial gas turbines andship gas turbines so as to reduce the pollutant discharged into atmosphere.