Chitosan films were corsslinked with sodium termetaphosphate and blended with SiO-2, and tested with tension machine. The results showed that the tensile strength of the composite preservative films was considerately improved, and when the concentration of chitosan was 1.2×10-4~1.4×10-4 mol/L, the sodium trimetaphosphate content was 0.08% and m-SiO-2∶m-chitosan was 0.15, the film's comprehensive mechanical properties is the best.