The invention relates to an online multifunctional operating device for a filling layer of a ballastless track board, and the operating device is capable of realizing automatic mixing filling of self-compacting concrete and belongs to the technical field of high speed railway construction. The online multifunctional operating device comprises a frame, a travelling system, a weighing platform, a mixing tank and a filling system, wherein the frame is compact and light in structure; when having no load, the frame can be conveniently pushed by a person, and the travelling direction of the frame can be fixed or freely changed; the frame is provided with weighing sensors which can be used for feeding back the amount of residual material in the mixing tank in real time, so that the filling speed and the filling amount can be controlled according to the residual material, secondary mixing can be carried out according to the amount of the residual material, and material waste is effectively avoided; the mixing tank is internally provided with concentric mixing blades with different diameters, so that variable frequency stepless speed regulation can be realized, and the requirements of secondary mixing can be met; the mixing tank is arranged on the weighing platform and is located by a limiting device, so that filling working conditions along the middle direction and the side direction can be met; the opening degree of a pneumatic gate valve is controlled by a PLC, so that the filling speed is controlled; therefore, the whole device has the functions of mixing as required and automatically filling, the material waste is reduced, and the filling quality of the self-compacting concrete is improved.