A novel anti-impact and flame retardant gel (AFG) was developed by combining ammonium polyphosphate (APP) with shear stiffening gel (SSG). AFG-55% (containing 55% of APP) exhibited excellent thermal property which the peak heat release rate of AFG-55% decreased by 57.48% compared with neat SSG. Its UL-94 vertical burning test reached V-0 rating. The flame-retardant mechanism was attributed to the ammonia and water molecules production during APP degradation which diluted the combustible gases and formed a char layer to block the flame. Besides, AFG effectively dissipated impact force from 768 to 204 N, showing excellent safeguarding properties for protecting human beings from harsh impact. Finally, a functional conductive AFG-55%-based fire warning sensor (FWS) with rapid alarm time of 5 s was developed. FWS stably alarmed the fire even after impact and cutting. Thus, this work proposed a novel AFG-55% polymer with enhanced thermal and safeguarding properties which showed promising application in flame retardance, fire suit and safeguards.