The two groups of Ca films were directly and respectively deposited on Si(100) substrates by Radio Frequency (R.F.) magnetron sputtering system (MS) and subsequent were annealed at 600°C for 5h, 6h, 8h, 10h and 12h in a vacuum furnace. The structural and morphological features of the resultant films are tested by XRD, EDAX and FT-IR. The cubic phase Ca2Si film is grown selectively from Ca-Si system of the existence of multiple silicide phases by an interdiffusion reaction of solid phase between the deposited particles and clusters and substrate constituents. And, the structure of the deposited films, annealing temperature and annealing time are the principal factor for the selective growth.