The invention relates to chromium nickel alloy powder for a flux-cored wire, the flux-cored wire and a preparation method of the flux-cored wire. The chromium nickel alloy powder comprises the following components of, by mass, 37-45% of Cr, 18-23% of Ni, 0.03% or less of C, 1.0% or less of the Si, 2.5% or less of Mn, 0.02% or less of S, 0.025% or less of P, 0.5% or less of Cu, 0.5% or less of Mo and the balance Fe. By adding the chromium nickel alloy powder in the flux-cored wire, drawing of a small-diameter welding wire is facilitated, and a large-diameter welding wire does not need to be subjected to heat treatment firstly; and meanwhile, in welding, the flux-cored wire is more even and stable, and splashing is effectively reduced.