The invention relates to a drive-by-wire brake system with a redundancy function. The drive-by-wire brake system comprises a drive-by-wire brake in modular design, a brake pump shell, a liquid storage chamber, a first spring, a first piston assembly, a check ring, a rubber ring, a second spring, a second piston assembly, a brake pedal, an angle sensor and a controller; wherein the drive-by-wire brake comprises a brake disc, a left friction plate, a right friction plate, calipers, an electromagnetic coil, a cylinder body assembly, a brake pipeline, a hydraulic control unit, a brake piston, a magnetostriction rod and a wheel speed sensor. In the invention, the magnetostriction actuator is adopted as a power source of the electronic mechanical braking system, the energy accumulator device is adopted, the braking clearance can be rapidly eliminated, the braking response time is shortened, and high braking control precision and response frequency are achieved; thus, even if the electronic mechanical braking system fails, the vehicle can still be braked by means of a conventional hydraulic braking system, and the reliability is high; in addition, the braking distance can be effectively shortened, and the vehicle driving safety is improved.