In order to study the relationship between the anti jet liquid density of periodic cell structure liquid composite armor and intracellular liquid density, in this paper, theoretical analysis and LS-DYNA finite element simulation were adopted to study the effect of different liquid densities on jet penetration, and the theoretical relationship between liquid density and the radial reaming of jet and the radial convergence of liquid, and the simulation results of jet interference were obtained. The results show that with the increase of liquid density, the jet reaming radius decreases, the radial convergence is enhanced, the breaking time is delayed, the interval of the velocity being disturbed decreases, and the residual penetration capacity increases. The simulation results coincide with the theoretical analysis from the viewpoint of energy dissipation.