The invention relates to an antibacterial finishing agent and a preparation method and antibacterial application thereof. The antibacterial finishing agent is a hybrid material aqueous solution loaded with silver sulfide nano-particles and is composed of a hybrid material loaded with silver sulfide nano-particles and water, wherein the hybrid material is composed of carrier molecules A, stabilizer molecules B and silver sulfide nano-particles. The preparation method comprises the following steps: stirring and mixing an aqueous solution of A and an aqueous solution of B, regulating the pH value of the mixed solution, sequentially dropwise adding a silver ion salt solution and a metal sulfide sulfur source aqueous solution into the mixed solution, and stirring, thereby obtaining the hybrid material aqueous solution. The silver sulfide nano-particles in the hybrid material loaded with the silver sulfide nano-particles are stably and effectively connected to a molecular chain of the carrier molecules in forms of ionic bonds and coordinate bonds. The water soluble antibacterial finishing agent is very stable, is high in dispersity and has an excellent broad-spectrum antibacterial effect. Moreover, cotton textiles treated by the using method have extremely high inhibition rate on multiple bacteria after standard soaping of over 20 times.