The development and enlargement of addressable magnetic core-shell hetero-architectures in a simple and economic way still remain a synthetic challenge. Herein, photofunctional magnetic FT1 (Fe3O4@TiO2 particles with 120 nm size) and FT4 ((Fe3O4@TiO2 particles with 420 nm size) core-shell particles with controlled size were fabricated successfully via a simple surface modification process that induces the atomic layer deposition (ALD) method. The size control of photofunctional magnetic particles has been adjusted by controlling the ratio of V(EG)/V(DEG) during the solvothermal reaction. Photocatalytic ability examination of the FT1 and FT4 core-shell particles was carried out in Rhodamine B (RhB) solutions illuminated under Xe light in a photochemical reactor. The photocatalytic activity depending on particle size indicates that the small FT1 particles are superior to the large FT4 particles due to the large surface area.