Exploring large and tunable magnetic anisotropy (MA) in a single magnetic atom is of merit for information storage due to the highest information data density. In this work, we studied the MA of transition-metal atoms X (X = Co, Fe, Ir, Mo, Nb, Ta, Ti, V, W) adsorbed on the surface of two-dimensional (2D) ferroelectric (FE) In2Se3 by first-principles calculations. We find that when the ferroelectric polarization of the In2Se3 is switched, the strengths of the MA for Co, Ir, Nb and Ti single atoms can be changed, while the directions of the MA for Fe, Mo, Ta, V and W single atoms are reversed. Calculated electronic structure and orbital-resolved magnetic anisotropy energy suggest that the variations in the occupation of spin-minority state and the exchange splitting of d orbitals at Fermi level by switching FE polarization are responsible for the change of the strength and direction of the MA on X atoms.