Liquid carboxyl terminated polybutadiene(CTPB) was aged at various temperature and analized for the physicochemical properties. The CTPB properties were degraded with the aging time and temperature. CTPB ther-mal degradation was observed due to the decomposition of carboxyl functional group situated at the end of butadiene chain. The activation energy for carboxyl group decreasing rate from arrhenius plot was found to be 19.5kcal/mole. Solid composite propellants were manufactured with aged CTPB and mechanical properties and gel contents were tested. The mechanical properties of propellants decreased with the degree of CTPB aging condition, because the reac-tivity of aged CTPB was reduced.