The invention discloses a self-protection type flux-cored wire for welding of G520 stainless steel and 25Cr2Ni4MoV alloy steel. The self-protection type flux-cored wire comprises a flux core and a welding scale. The flux core comprises the following components of, by mass, 1%-4% of ferrosilicon powder, 3%-5% of manganese powder, 15%-20% of chromium powder, 12%-16% of nickel powder, 7%-9% of copperpowder, 2%-5% of ferrocolumbium powder, 8%-13% of rutile powder, 13%-15% of fluorite powder, 6%-10% of zircon sand powder, 4%-8% of lithium carbonate powder, 3%-5% of ferric oxide powder, 3%-5% of alumina powder, 4%-5% of magnesium oxide powder, and the balance iron powder, and the sum of the mass percentages of all the above components is 100%. Compared with a stainless steel welding rod and a solid welding wire, the prepared flux-cored wire flux-cored wire has the advantages of little welding spattering, attractive weld joint forming and good welding process performance and can be used fora continuous wire feeding automatic welder, a preparation method is simple, operation is convenient, and the preparation method can be used for mass production.