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 degrees C. The PST thin films were crystallized at a temperature as low as 300 degrees C, which may result from the well-controlled stoichiometry and the in situ crystallization on seed layer. At an electric field of 400kV/cm, high tunability of 43% and 57% can be achieved for PST films deposited at 300 degrees C and 500 degrees 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.