The invention relates to a support device for demounting a spindle bearing of a thickener. The support device comprises a spindle (2), a connecting dowel (3) and a spindle bearing portion (4), a rake rack is arranged on the spindle (2), the spindle bearing (4) is arranged above the spindle (2), and the connecting dowel (3) connects the spindle (2) with the spindle bearing portion (4). The support device for demounting the spindle bearing of the thickener is characterized in that when the spindle bearing is demounted, the support device (1) is arranged between a support point (21) of the spindle (2) and an ore deposition layer at the bottom of a high-efficiency thickener tank so as to support the spindle (2) and the integral gravity of the rake rack and conveniently pull out or insert the connecting dowel (3) so that the spindle (2) and the spindle bearing portion (4) are enabled to be separated or connected, and accordingly, the spindle bearing can be demounted or mounted. The support device (1) comprises a support body (12) and a handle (11), wherein the support body (12) is of a cylinder structure made of common round steel, and the handle (11) is arranged on the lateral side of the support body (12).