Thermal insulation layer in solid rocket motors is a vital component during the rocket flight. Many factors can affect the performance of this insulation layer. Bonding property between rocket propellant and the thermal insulation layer are examined in this study. Hydroxyl terminated polybutadiene (HTPB) and isophorone diisocyanate (IPDI) as a curative was chosen as the most common type of rocket propellant. The effect of two types of polymeric insulation layer such as nitrile butadiene rubber (NBR) and ethylene-propylene-diene monomer (EPDM), on the bonding performance at the interface between (HTPB/IPDI) propellant and the respective insulation layer has been investigated. Results revealed that both types of insulation layer considerably decreased the interfacial bonding performance of the (HTPB/IPDI) propellant. NBR was proven to be more severe on weakening the adhesion strength than that of the EPDM. We further investigated the effects of the thickness and water content of NBR on the bonding performance, and proved that bonding strength was inversely proportional to the thickness and the water content.