This project studied a preparation of alumina reinforced epoxidized natural rubber (ENR) by latex compounding. A purpose of this study is investigating the possibility of alumina latex compounding and studying properties of alumina loading epoxidized natural rubber. The factors such as alumina content, epoxidation and alumina particle size, affect to properties of composite was determined. In addition, comparison of solid state mixing and latex mixing was done. Epoxidized natural rubber latex was prepared from in situ epoxidation of natural rubber and, formic acid and hydrogen peroxide at 60°C for 8 h. Different degree of epoxidation was obtained by varying mole ratio of formic acid and hydrogen peroxide to natural rubber. Then, compounding of ENR latex with vulcanizing chemical was performed. The optimum compounding condition and maturation were evaluated. It was found that suitable maturation was 1 day and stirring at 600 rpm for 1 h gave a good alumina dispersion. Furthermore, the composite with different alumina content was prepared. It can be observed that alumina was regularly dispersed in ENR matrix. The agglomeration to a bigger particle was obtained at the higher alumina content. Hardness, modulus at 100 and 300% elongation increased as alumina content was increased, while resilience decreased. Maximum tensile strength of composite was obtained at 10 phr alumina added. Thermal stability and Tg(DSC) increased as alumina loading increased, meanwhile, swelling ratio decreased. Furthermore, the effect of epoxidation was determined as well. It was found that alumina precipitate onto mould in case incorporated in NR latex because of low compatibility. At higher epoxidation, alumina loading was limited as well due to film cracking. This result could be the synergist effect of rigidity of epoxide structure and hardness characteristic of alumina. In ENR composite without alumina, a high epoxidation rubber shows a lower Tg(DMTA) than a low epoxidation rubber. Meanwhile, ENR with alumina, Tg increased as degree of epoxidation increased. This caused by the occurring of interaction between alumina and epoxide groups, therefore, chain mobility decreased. Alumina particle size affect to mechanical properties as well. It was found that smaller alumina gave a higher tensile strength and hardness. In solid state mixing, it confirmed that alumina was more compatible with ENR than NR. It resulted a better particle distribution and a higher tensile strength. Swelling ratio of alumina filled ENR dramatically decreased compared to unfilled ENR. This caused by alumina-epoxide interaction. Whereas, swelling ratio NR composite slightly decreased. Comparison of solid state and latex mixing, it shows that solid state mixing had a higher mechanical properties because of a different vulcanization mechanism affected different vulcanization efficiency.