Mechanical properties of natural rubber film prepared from latex was improved by adding modified silica. Precipitated silica was modified by admicellar polymerization with polyisoprene coating for improving the dispersion in natural rubber latex. The coated polyisoprene film on silica surface was around 15±5% by weight. Modified silica was characterized by FT-IR and SEM. The suspensions of silica and other chemicals were prepared before mixing with natural rubber latex. The particle size and time for dispersion of all chemical suspensions were investigated. The latex after mixing with all suspensions was used to measure the pre-vulcanization by swelling degree testing. The rubber film was formed by dipping process from the mixed latex. Lastly, the mechanical properties of rubber film was examined. The results show that the mechanical properties of the rubber film by adding modified silica had the improvement comparing with pure rubber and adding unmodified silica latex.