The present invention belongs to the field of olefin polymerization, and specifically provides a chromium-based catalyst component and a preparation method thereof, and a chromium-based catalyst. The chromium-based catalyst component comprises the reaction product of components such as a chromium compound, an oxide carrier and an organic boron compound, wherein the organic boron compound is a compound having a structure represented by a formula 1, and R<1>-R<5> are respectively selected from hydrogen, a halogen, linear chain and branched chain C1-C20 alkyl or haloalkyl, linear chain and branched chain C1-C20 alkoxy or haloalkoxy, linear chain and branched chain C2-C20 alkenyl or haloalkenyl, and the like. According to the present invention, with the application of the chromium-based catalyst in ethylene polymerization, the high polymerization activity can be provided, and the prepared polymer has broad molecular weight distribution and high melt index. The formula (1) is defined in the specification.