In order to study the influence of liquid parameters on the protective performance of liquid composite targets (LCT), based on the theory of interaction between the jet and the LCT, three dimensionless numbers - C, G, and V - are obtained by dimensional analysis in this paper. These 3 dimensionless parameters represent the compressibility, inertia, and viscosity of the liquid, respectively. The empirical formula, P/H = 0.346C1.251G−0.7120V0.036, was obtained by fitting experimental data of the static depth of penetration (DOP) experiment which can predict the residual depth of penetration (RDOP) of the jet penetrating the LCT. It turns out that the 2 dimensionless parameters - C and G - which characterize the compressibility and inertia of the liquid, plays a decisive role in the protection performance of the LCT, while the influence of liquid viscosity is small. In addition, according to the research results of this paper, the protective performance of the LCT can be improved by selecting a liquid with high sound velocity, high viscosity, and low density.