The steering ratio characteristic is one of the research key points of steering by wire (SBW) system due to the decoupling of mechanical linkages between front tires and the steering wheel of SBW vehicles. This paper focuses on the characteristic that the steering ratio of SBW system can be designed flexibly and proposes a series of design strategies for the steering ratio system in the light of the stable steering characteristic and transient steering characteristic of vehicles. Aiming at the stable steering characteristic of vehicles, a set of design bases is proposed in order to improve the handing stability for vehicles at low velocity section, middle velocity section and high velocity section respectively, and then deducing three variable steering ratio design strategies for SBW vehicles corresponding to different velocities, the simulation results show that the steering ratio system for the vehicle at stable steering state can meet the handling demand at every velocity section. Aiming at the vehicle transient steering characteristic, this paper advances a compensation strategy based on the electronic stability program (ESP) to compensate the front wheel angle, in order to decrease the yaw rate at transient steering state and reduce the possibility of vehicle instability, the simulation results show that this strategy can improve the driving safety for vehicles at transient. Finally, a steering characteristic pattern recognition model to recognize the steering characteristic of vehicles is built based on the hidden Markov model (HMM), so that the corresponding steering ratio system can be invoked on the basis of recognition results. The test results of maximum likelihood function show that the steering characteristic recognition model has a nice recognition effect of the steering characteristic.