The invention discloses an optical fiber F-P filter and a preparation method thereof, and solves the problems that translational dislocation and even inclined angle are liable to occur in the end surface processing course of the present optical fiber F-P cavity so that cascade spacing of the optical fiber F-P cavity can be reduced and miniaturization of the cascade filter can be realized. The adopted technical scheme is that two or more than two micron-scale holes are continuously carved on one optical fiber core in one step by using the excimer laser to manufacture a single optical fiber F-P filter or a cascade optical fiber F-P filter, the optical fiber end surface is replaced by the micron holes and the air medium is replaced by the optical fiber core so that transmission light is enabled to be reflected for multiple times between the micron holes to form interference, a pair of micron holes form the single optical fiber F-P filter, and multiple micron holes form the cascade optical fiber F-P filter.