Soybean (Glycine max L.) is a bean plant that has long been known and cultivated in Indonesia. The damage to soybean seed during storage due to post harvestpest such as Callosobruchus maculatus F. causes damage to 80%. An alternative method to control post harvest pest is by using rhizome alang-alang powder. The purpose of this research was to get the effective dose of alang-alang rhizome powder to control C. maculatus F., so as to maintain the quality of soybean seed during storage. A laboratory experiment was conducted with 6 treatments and 3 replications, and arranged in Completely Randomized Design (CRD). The treatments which used in this research were: 0 grams of alang-alang rhizome powder (control), 10 grams of alang-alang rhizome powder, 20 grams of alang-alang rhizome powder, 30 grams of alang-alang rhizome powder, 40 grams of alang-alang rhizome powder and 0,9 mg phostoxin (syntetic pesticides). Results showed that 10 gram of alang-alang rhizome powder was effective to control the C. maculatus F., with 100% efficacy value. However, the rhizome alang-alang powder could not control the development of new generation C. maculatus F., and also could not yet maintain the quality of soybean seeds up to 2 months of shelf life.