Highly (100) oriented lead strontium titanate (Pb0.4Sr0.6TiO3) thin films were deposited on LaNiO3 -coated Si substrate via radio-frequency magnetron sputtering method with substrate temperature ranging from 300 to 500°C. The PST thin films were crystallized at a temperature as low as 300°C, which may result from the well-controlled stoichiometry and the in situ crystallization on seed layer. At an electric field of 400 kV/cm, high tunability of 43% and 57% can be achieved for PST films deposited at 300°C and 500°C, respectively. Moreover, the dielectric response shows weak frequency dependence and the loss factor stays relatively low. The results suggest that such films should be promising candidate for the microwave tunable devices compatible with the current Si technology.