Using poly(acrylic acid) (PAA) as a template, a novel Fe3O4@C@TiO2 yolk-shell structure derived from heat treatment on Fe2O3@PAA@TiO2 core-shell structures is constructed, where the interior void volume and shell thickness are readily tuned. In this method, the PAA shell between the original spherical α-Fe2O3 nanoparticle (NP) core and the outer TiO2 shell replaces the common SiO2 template leaving out the tedious treatment procedure of the template. After calcination, the α-Fe2O3 core was reduced to the Fe3O4 core providing the NPs with magnetic properties and the middle carbon coating around the magnetic core could avoid the occurrence of photodissolution. Moreover, the obtained Fe3O4@C@TiO2 yolk-shell nanocomposites (NCs) exhibit fine photocatalytic activity for the photodegradation of organic contaminants in waste water.