The invention relates to the technical field of mechanical manufacturing equipment, in particular to a flexible grinding wheel for forming the outer contours of steel rails, a grinding device with the flexible grinding wheel and a steel rail milling and grinding trolley. The flexible grinding wheel comprises a flange and a plurality of forming grinding wheel blocks, wherein the forming grinding wheel blocks are evenly distributed on the external circumference of the flange, all the forming grinding wheel blocks and the flange are located on the same rotation plane, and each forming grinding wheel block is connected with the flange through a reset mechanism so that each forming grinding wheel block can move in the direction perpendicular to the axis of the flange. When the flexible grinding wheel is used for grinding, it can be effectively avoided that because the sleepers of steel rails are not compacted and joints exist on the steel rails, when wheels pass by, the amount of vertical deformation of the steel rails is large, grinding is discontinuous because of the affection, and the grinding amount is too large or too small because of the affection; and therefore, it is guaranteed that even if under the road conditions that the sleepers are not compacted, steel rails are seriously abraded, smoothness is poor, and joints exist on steel rails, the requirements on the forming grinding quality of the outer contours of steel rails can still be met.