The invention relates to the technical field of transmission in mechanical engineering, in particular to a speed-adjustable magnetic concentrating double-cylinder asynchronous magnetic coupler. The magnetic coupler is composed of a driven rotor assembly, a driving rotor assembly and a speed adjustment device assembly. Permanent magnets are closely stuck on the outer surface of an inner matrix and the inner surface of an outer matrix of a driven rotor. Every two adjacent permanent magnets constitute a magnetic pole, wherein one magnet is magnetized in the radial direction, and the other magnet is magnetized in the tangential direction. The adjacent surfaces of the magnets magnetized in different directions tilt by an angle of alpha. Fan-shaped transparent slots are machined at an interval of certain radian along the circumference of a copper ring. Cast iron blocks with the same shape as the fan-shaped transparent slots are embedded into the slots. Threaded holes are machined in the sides of the copper ring and the cast iron blocks. The cast iron blocks are fixedly connected with the copper ring through countersunk head screws. A servo motor works and drives a double-headed cylindrical cam to rotate. The cylindrical cam drives left and right driven rotors to move along a connecting rod in the same direction or in opposite directions through a sliding rod. Thus, the relative meshing area of the permanent magnets and the copper ring is changed. The speed adjustment function of the magnetic coupler is achieved.