The present invention relates to a reinforced fiber used in papermaking, a preparation method thereof and a paper product containing the fiber. The present invention first provides the reinforced fiber used in papermaking, which is produced by the spinning of the following materials: 80wt percent to 99.95wt percent of polyvinyl alcohol and 0.05wt percent to 20wt percent of modifier; and wherein, the modifier contains one or more of polyamide type, cellulose type, polyamine type and quaternary ammonium salt type high-molecular polymers. The present invention also provides the preparation method of the reinforced fiber and the paper product containing the reinforced fibers. By adding the modifier into spinning stock solution, the obtained reinforced fiber can have more reactive active functional groups, and thereby, the hydrophilicity and wettability of the surface of the reinforced fiber can be enhanced. The reinforced fibers, which are uniformly mixed with paper pulp for papermaking, can notably improve all the intensity indexes of the produced paper product.