Two groups of silicon carbide ceramics were prepared by pressureless sintering processing with a small amount of boron and carbon as sintering additives. The flexural strength, Vickers hardness, fracture toughness and compressive strength of the samples were measured and compared. Sample A achieved much higher flexural strength (389.4MPa) than that of sample B (250.3MPa) due to the difference of additive dosage. However, the two groups of samples attained comparable values for the other three mechanical properties. SEM observation revealed that the stoichiometric ratio of the Si/C atom in the sintered body is an important factor to affect the mechanical performance of the silicon carbide. The ballistic performance of the samples was also evaluated in this study. The results showed that sample B exhibited more excellent ballistic property, which is probably related to the high flexural strength. The detailed influencing factors need to be studied further.