In this paper, the SiCx thin films with silicon quantum dots were prepared by RF and pulse magnetron co-sputtering and rapid thermal annealing. The films were characterized by grazing incidence X-ray diffraction, Raman spectroscopy, UV/VIS/NIR spectrophotometer and transmission electron microscopy. The effects of pulse sputtering power on the number, size and crystallization rate of silicon quantum dots in the films and the optical bandgap of the films were investigated. The results show that with the increasing of sputtering power from 70 W to 100 W, the number of silicon quantum dots increased; the size increased to 5.33 nm; the crystallization rate increased to 68.67%; the optical band gap reduced to 1.62 eV. When the sputtering power increased further to 110 W, the number of silicon quantum dots reduced; the size reduced to 5.12 nm; the crystallization rate of thin film reduced to 55.13%; the optical band gap increased to 2.23 eV. In this experiment, the optimized sputtering power was 100 W.