Abstract: Silicon carbon composite (Si/C) films with different silicon and carbon contents were deposited on copper foil by magnetron sputtering and used as cathode materials for lithium-ion batteries. The electrochemical properties of silicon carbon content ratios of 1.26, 0.72, 0.52, 0.45 and 0.39 were explored. The experimental results show that when the silicon content is high and the carbon content is low(Si/C=1.26), the first discharge specific capacity is the highest (3 089.50 mAh·g^-1), but the capacity retention rate after multiple cycles is the lowest (46.83%). When the carbon content is high and the silicon content is low (Si/C=0.39), its discharge specific capacity is relatively stable, but its discharge specific capacity is the lowest. When the silicon carbon content ratio is close to 0.5 (Si/C=0.52), its rate capability is the best and the capacity retention rate after multiple cycles is the highest(61.73%). In addition, the three cycles of CV curves of this sample are almost consistent, indicating that it has good cyclic stability, at the same time, it has a low internal resistance (5.98 Ω).