In this paper, the focusing effects of the Pearcey beam (PB) are improved based on catastrophe optics, and the Pearcey integral is modified based on the butterfly catastrophe light field. A modified Pearcey beam (MPB) with a long focal depth is proposed, and the flexible adjustment of the focus position of the MPB is realized through theoretical analysis, simulation and experiment. The long focal depth of the beam is achieved under the premise of keeping the stable focus of the beam. Compared with the PB, the MPB has longer focal depth and more flexible focus position. With improved focusing effects, the applications of the MPBs in optical imaging and optical manipulation can be expanded.