The invention discloses a method for reducing molded inner cracks of temperature-sensitive type PBX with a large length-diameter ratio. Based on the technological base of a developed die pressing molding technology, a temperature inverse compensation method is introduced; the temperature of a base is higher than that of a mold sleeve; the temperature of the mold sleeve is higher than that of an upper punch; the temperature difference value between the temperature of the base and the temperature of the mold sleeve, and between the temperature of the mold sleeve and the temperature of the upperpunch, i.e., a temperature gradient, is greater than 5 DEG C and not higher than 15 DEG C. The method disclosed by the invention mainly adopts a combined temperature inverse compensation method; the temperature of the base is improved so that the temperature of the base is higher than the temperature of the mold sleeve and the temperature of the mold sleeve is higher than the temperature of the punch. By adopting the temperature compensation method, thermal stress caused by temperature difference between upper and lower end faces in a propellant grain molding process is reduced; furthermore, effective pressure, which is reduced due to friction, on a propellant grain with the large length-diameter ratio is further properly compensated. The method can be used for reducing the inner cracks ofthe propellant grain, and also can be used for effectively improving the uniformity in the propellant grain.