The invention relates to the technical field of liquid rocket engines, and particularly relates to a mixed injector and a small liquid rocket engine. The mixed injector comprises a shell, a cover plate and a core, wherein an oxidant cavity and a fuel cavity are formed in the shell; the oxidant cavity is annular, and the oxidant cavity surrounds the fuel cavity; the cover plate covers the upper endsurface of the shell and is welded with the shell and is used for sealing the oxidant cavity; the core is arranged in the fuel cavity, and fuel in the fuel cavity can be rotational and centrifugal bythe core; and a panel is arranged on the lower end surface of the shell, a fuel nozzle and an oxidant nozzle are formed in positions, which correspond to the fuel cavity and the oxidant cavity, of the panel, the fuel which is rotational and centrifugal in the fuel cavity by the core is sprayed by the fuel nozzle, and oxidant in the oxidant cavity can be sprayed by the oxidant nozzle. According tothe mixed injector, the core structure of the fuel nozzle is additionally arranged, so that the centrifugal spraying of the fuel is realized, the mixed injector and a straight-flow oxygen nozzle forma mixed spraying mode, the atomization effect is good, and the combustion efficiency is high.