The invention discloses a method for continuously and quickly preparing a SiC fiber surface BN coating. By utilizing a yarn winding and unwinding device, after a SiC fiber is subjected to amorphous form BN interface deposition under movement, the crystal-state BN coating can be directly converted, so that the problem that in the prior art, no amorphous form BN is decomposed during a deposition-heat treatment conversion process is effectively avoided. A microwave heating manner is adopted during a heat treatment process, so that a uniform and flawless stable crystal structure is finally obtained; and in addition, the yarn winding and unwinding device adopts a multi-roller system, so that cyclic deposition is carried out during a deposition process, and the crystal-state BN coating with therequired thickness can be quickly obtained.