Novel geminal dinitro ester energetic plasticizers (DNEPs) were designed with different alkane lengths in the mainchain, namely 2,2-dinitropropyl acetate (DNPAc), 2,2-dinitropropyl propionate (DNPPc), and 2,2-dinitropropyl propionate (DNPBc). Due to the incorporation of ester and dinitro groups, these three DNEPs were expected to possess high heat of formations and thermal decomposition temperatures (T-p) and lower glass transition temperatures (T-g). Likewise, their impact sensitivities were all measured as higher than 25.2 J. Due to the maximum alkane length of DNPBc, DNPBc possesses the highest T-p and the lowest T-g. As plasticizers for glycidyl azide polymer (GAP), DNEPs significantly improve the viscosity and T-g of GAP. Particularly, the plasticizing efficiency of DNPBc is higher than that of the reported N-butyl nitroxyethyl nitramine (BuNENA). Likewise, the specific impulses of GAP/HMX based compositions with DNEPs as energetic plasticizers were all slightly higher than that of BuNENA. Therefore, these DNEPs (especially DNPBc) exhibit promising potential as candidates for replacement of BuNENA in GAP based propellants.