The invention relates to a steering-mode adjustable electric automobile steering system and a control method. The steering-mode adjustable electric automobile steering system comprises two motors, a mechanical steering module, an electric assisting steering module and a steering-by-wire module, wherein the two motors are arranged on a steering column and a steering pinion respectively, the mechanical steering module, the electric assisting steering module and the steering-by-wire module are formed by three electromagnetic clutches and the like and are used for mechanical steering, electric assisting steering and steering-by-wire. The control method mainly includes the first step of carrying out system initialization, the second step of allowing an ECU to start the corresponding steering mode and carrying out control according to the steering mode selected by a driver, the third step of controlling the steering modes, and the fourth step of carrying out fault diagnosis and fault-tolerant control on the steering system. The steering-mode adjustable electric automobile steering system and the control method have the advantages that the same automobile has high control flexibility on the precondition of being simple in structure, and consequently switching of driving modes can be achieved; when one motor breaks down, an original steering mode can be switched to a steering column assisting type electric assisting steering mode or a pinion assisting type electric assisting steering mode or a mechanical steering mode, and consequently the operation stability, reliability and the fault-tolerance capacity of the automobile are improved.