The principle and realizable approach of variable-burning rate propellant, the burning rate of inner layer is higher than that of the outer layer are introduced. The combustion character of two layered variable-burning rate propellant in closed bomb test is analyzed and the interior ballistic performance on 30mm gun is construced. Contrast with single base gun propellant with polymer coating layer, the two-layered variable-burning rate propellant has good properties of progressive combustion and low temper...