Abstract: Disclosed is a power assist anti-tip wheel system for invalid carriage including at least one connecting support, at least one assist anti-tip wheel, and at least one power driving means. The connecting support is fixedly or detachably connected at one end to a front or a rear side of the invalid carriage. The anti-tip wheel is associated with the connecting support so that it is located in front of or behind the invalid carriage. The power driving means is also associated with the connecting support to drive the anti-tip wheel to rotate when the invalid carriage travels onto a slope or passes a recess or a bulge on a road surface and two drive wheels thereof become suspended and idling. The power driving means can be automatically actuated via a sensing circuit or be manually actuated via a push button.