Abstract: The relationship between the ballistic coefficient and the static mechanical properties of armor materials was studied. The results show that the ballistic coefficient is determined by the strength, hardness and the toughness of materials. According to the Martel rule, the equation of the relationship between ballistic coefficient and static mechanical properties satisfies the following formula: \W_\rms = M(1 + N\fracK_\rmIC\rho )H_\rmT\. From the mixture law of composite, the prerequisite, for which ballistic coefficient has maximum to reinforcement volume fraction, is obtained by the following equation: \\frac\rmdW_\rmS\rmdf = b(K_1\rho _0 - K_0\rho _1)\fracH\rho ^2 + (a\fracK\rho )(H_1 - H_0)\.