The invention relates to the technical field of microfluidics and discloses a microfluidic assembly, a microfluidic chip and a preparation method thereof. The microfluidic assembly comprises a first base plate and an opposite base plate which are oppositely arranged to form a micro-cavity; the first base plate comprises a first substrate and a flexible substrate layer arranged on the side, facingthe opposite base plate, of the first substrate; columnar microstructures in array distribution are arranged on the surface of one side, far away from the first substrate, of the flexible substrate layer, and magnetic materials are arranged at the top ends of the columnar microstructures; the first base plate also comprises an electromagnetic structure arranged on the side, far away from the opposite base plate, of the flexible substrate layer and is configured to generate a magnetic field in an electrified state to drive the magnetic material to drive the top ends of the columnar microstructures to deviate. The microfluidic assembly can improve the liquid drop moving continuity and flexibility.