The energy parameters of the propellant containing octanitrocubane（ONC） are calculated by CAD system of propellant energy calculation under standard condition（p_c/p_o=70∶1）. Replacing ammonium perchlorate with octanitrocubane in HTPB propellant increases the specific impulse for 125 N·s·kg^-1，NC/NG/ONC smokeless MDB propellant has a specific impulse of 2545 N·s·kg^-1，GAP/ONC/RDX smokeless propellant has a high specific impulse over 2600 N·s·kg^-1 in very wide scope.