The invention relates to a formula for reducing high pressure exponent of solid propellant and improving the performances of a rocket engine fuel. The formula is characterized in that 20-30% of an adhesive and a plasticizer, 0-15% of an oxidant ammonium perchlorate (AP), 30-45% of nitramine explosive, 10-30% of insensitive high explosive FOX-7 with the granularity of 8-200 [mu]m, 1.0-2.0% of a curing agent and 0.5-2% of a combustion stabilizing agent are added to a solid propellant system. The insensitive high explosive FOX-7 with good dispersibility and component compatibility, the AP, the adhesive and the plasticizer are used to guarantee the signal characteristic and the energy, technology and mechanical performances of the propellant, reduce the high pressure exponent of the propellant and guarantee the working reliability of an engine. The formula has the advantages of scientific formula, convenience in production, obvious effect and stable performances.