The invention provides a multipurpose combined type annular ram preventer which comprises a ram preventer body, a well mouth valve assembly, an annular space injection device, a well mouth lower flange and a casing nipple. The upper end of the ram preventer body is connected with the well mouth valve assembly through a flange, the lower end of the ram preventer body is fixedly connected with the annular space injection device, the well mouth lower flange and the casing nipple from top to bottom in sequence, and the inner cavity of the well mouth valve assembly, the inner cavity of the ram preventer body, the inner cavity of the annular space injection device, the inner cavity of the well mouth lower flange and the inner cavity of the casing nipple are communicated. The height of a well mouth is lowered, waste of resources is reduced, site construction environment is improved, and certain potential safety hazards are eliminated. Meanwhile, the problems that resistance is large, a tubing coupling is difficult to lay down, an annular rubber core is seriously damaged when the tubing coupling is laid are solved through decompression and a balance valve group.