The invention discloses a precipitation hardening stainless steel flux-cored wire for continuous roller submerged arc overlaying and a preparation method thereof. The flux-cored wire consists of chemical powder and an external carbon steel strip; the chemical powder is 35.0-38.0% of the total weight of the wire; and the chemical powder comprises the following components in percentage by weight: 29.0-31.0% of metal chromium powder, 25.0-26.5% of low-carbon ferrochromium, 12.0-13.0% of metal nickel powder, 10.0-11.5% of metal copper powder, 0.8-1.2% of electrolytic metal manganese, 1.0-1.5% of ferroniobium, 0.1-0.8% of metal molybdenum powder, 0.3-0.6% of ferrotitanium, 2.0-2.5% of rare earth ferrosilicon, 0.3-0.6% of metal aluminum powder, 8.0-10.0% of barium fluoride, and the balance ironpowder. In the flux-cored wire, an overlaying layer achieves excellent wear resistance, corrosion resistance, cold and hot fatigue resistance and tempering softening resistance, so that the service life of continuous rollers can be prominently prolonged.