It¡¦s easy to get the complication of shoulder by using the traditional type of driving a wheelchair, and the move speed of a wheelchair is upper with motor-driven, so makes shimmy or slide usually appearing on caster when the wheelchair is steering .On the other hand, the drive mechanism of wheelchair by single-wheel was developed by the members of MEVL at the same time that this paper was written. Because of these reasons above, this paper analyze the type of steering mechanism and the patents of wheelchair¡¦s steering mechanism first, secondly find the fittest steering mechanism type for a wheelchair. Furthermore, this paper also discusses some irregular conditions of a caster and theirs reasons and how to prove them when a wheelchair is steering or moving with high speed by using several simpler mode of mechanics, such as caster shimmy, the slip angle of a caster, and some irregular cases when wheelchair is driven by single wheel. Finally this paper will design a new type steering mechanism for wheelchair by applied the results of research that above-mentioned, this new steering mechanism not only improve the traditional steering mode of a wheelchair, also avoid several irregular condition above occurring in the caster, moreover, it can be enabled or disabled by user anytime. So this paper expects that the performance of a wheelchair will be raised after the new type steering mechanism is designed.