In order to study the self-extinguished solid propellants combustion performance and the pressurization-induced extinguished mechanism， HTPB/AOT/AP self-extinguished solid propellants were prepared by using sodium dioctyl sulfosuccinate （AOT） as extinguishing agent. Experimental characterization of propellants burning rates， combustion wave structure， flame morphology and flame quenching burning surface topography was carried out. The experimental results show that AOT reduced the pressure exponent below 10 MPa from 0.37 to -1.36， with the burning rate decreasing from 5.9 mm·s^-1 to 2.9 mm·s^-1 as pressure approached the critical extinguished pressure； AOT caused the propellant to self-extinguished when the pressure increased to 10 MPa， with unsustainable combustion observed at higher pressures. As the pressure approached the critical extinction pressure， a molten layer approximately 230 μm thick to cover the propellant burning surface， reducing the burning surface temperature from 865 K to 420 K and the gaseous phase temperature gradient from 74.9 K·μm^-1 to 0.19 K·μm^-1 compared to when pressure at 2 MPa. The pressurization-induced extinguished mechanism of self-extinguished solid propellant has been revealed， where​ AOT causes a thicker molten layer to cover the propellant surface， obstructing heat feedback from the gaseous flame to the burning surface， reducing burning surface temperature and condensed phase reaction rate， and ultimately resulting in extinguishing due to failure to maintain self-sustained combustion.