The invention relates to a 
brake-by-wire device with a redundancy function and a control method thereof. The device comprises a 
brake disc, 
calipers, a power take-off gear, a gear shaft, a lead screwshaft, an 
electromagnetic clutch, a nut 
assembly, a return motor, a motor support, a support, a 
brake oil cylinder, a right friction plate, a left friction plate, a first two-position two-way 
electromagnetic valve, a second two-position two-way 
electromagnetic valve, a vehicle speed sensor, a controller and a gear sensor. Vehicle 
kinetic energy can be fully utilized as a power source, a driving motor adopted in the prior art is omitted, and the cost is effectively reduced; a gear power take-off mechanism is used for driving an execution structure to generate braking force, and the braking force of a brake is controlled through the 
electromagnetic clutch. A redundancy function is realized through 
coupling with a conventional hydraulic 
braking system; the brake-by-wire device has the advantages of the high integration level, the high response speed and low cost; and when a vehicle is braked and locked, a hydraulic braking switch 
control mode is changed into a braking force continuous adjustable mode, and higher control precision is achieved.