The invention discloses a nano-silver sol special for gel and a preparation method of the nano-silver sol. The preparation method of the nano-silver sol special for gel includes the following steps ofdissolving carbomer in deionized water, properly adding an alkaline solution, and adjusting the pH value to be neutral to obtain a neutral carbomer solution with the mass concentration of 0.01-2 g/l;dissolving a silver salt in deionized water to obtain a silver salt water solution with the mass concentration of 0.001-10 g/l; dissolving sodium borohydride in deionized water to obtain a sodium borohydride water solution with the mass concentration of 0.001-1 g/l; mixing the neutral carbomer solution with the silver salt water solution, stirring the mixture uniformly, and dripping the sodium borohydride water solution during continuous stirring until silver ions are completely reduced into nano-silver particles to obtain the nano-silver sol special for gel. The silver salt component is oneor a mixture of silver nitrate and silver acetate. The alkaline solution is ammonia water or a diethanolamine solution or a triethanolamine solution. In this way, the nano-silver sol completely adoptscarbomer as a dispersing agent, auxiliary dispersing agents are not added, the system stability is high, and the nano-silver sol can be directly added into carbomer gel and is convenient to apply andpopularize in nano-silver antibacterial gel.