In the wheelchair family, a manual wheelchair is most commonly used by the lower-limb disabled, while its manual mode creates the lowest mechanical effi-ciency and the highest rate of upper-limb injury. Electric wheelchairs on the market are much more labor-saved; however, with their drive systems mostly combining with the bodies of the wheelchair, electric wheelchairs appear to be bulky and are not easily-carried. While in a limited space, on a short-distance moving, or in/off the elevator, electric wheelchairs cannot be practicably switched to manual ones. Thus, this text aims to develop a switchable dou-ble-action manual/electric wheelchair with an auxiliary driving wheel, expect-ing to increase the mechanical efficiency and not to enlarge the body of the wheelchair; the module-disassembled drive system is intended for the conven-ience of carrying. Besides, in order to keep both the manual and the electric functions, the caster contains a set of separable orientation control system, while enables the caster to be switched in both the modes of 360-degree rotation and of being controlled by the user. In this way, the use of the wheelchair would be-come much more multiple-choice.