The change of structure in the ternary system CaO-SiO2-TiO2 with TiO2 varying from 0 to 25% mole fraction at a fixed basicity of 0.8 was investigated by means of molecular dynamics simulation. The present simulation demonstrates that most Si is coordinated with 4 O within a tetrahedron while the majority of Ti with 6 O in an octahedron. With the addition of TiO2, the coordination number for Si (CNSi-O) changes from 4.12 to 4.03, while the CNTi-O varies from 5.83 to 5.52. The fraction of bridging oxygen (Si-O-Si) decreases resulting in the depolymerization of silicate structure and the Si-O-Ca is gradually replaced by Si-O-Ti with increasing TiO2 fraction. Two [TiO6] octahedrons are connected by two ways with the angles of Ti-O-Ti equaling to 100° and 140°, and the fraction of them are almost the same for sample with 10 mol-% TiO2 addition. The variation of network connectivity Q n of Si also agrees with the above conclusion. Thus, TiO2 is regarded as basic oxide which acts as modifier in this ternary system in terms of its structure within this system.