A reaction kettle comprises a kettle body (1) and a composite stirring device (2). The composite stirring device (2) is arranged at the top or the bottom of the kettle body (1) and comprises a solid stirring shaft (3) and a hollow stirring shaft (4), wherein the solid stirring shaft (3) and the hollow stirring shaft (4) both penetrate into the kettle body perpendicularly and are arranged on the central axis of the kettle body. At least two stirring paddles are installed on the solid stirring shaft (3) from bottom up, wherein the stirring paddle on the bottom layer is a radial stirring paddle (6), and the stirring paddle on the upper layer is an axial stirring paddle (5). A spiral stirring paddle or an anchored stirring paddle of the diameter is closed to that of the kettle is installed on the hollow stirring shaft (4), and the diameter of each of the stirring paddles on the solid stirring shaft is smaller than that of the stirring paddle on the hollow stirring shaft.