A method for preparing a nano-silver powder, characterized by comprising: dispersing 1 g to 15 g silver salt precursor in 10 mL to 120 mL solvent, to obtain a silver salt dispersion; dissolving 1 g to 60 g disperser in 10 mL to 200 mL solvent, to obtain a disperser solution, the disperser being an acrylic-modified polyurethane-based disperser for water and weak solvents, the weak solvents being one or more selected from the group consisting of ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, di-propylene glycol monomethyl ether acetate, di-propylene glycol monoethyl ether acetate, di-propylene glycol monobutyl ether acetate, propylene glycol monoethyl ether acetate, di-ethylene glycol monomethyl ether acetate, di-ethylene glycol monoethyl ether acetate, di-ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl ether acetate, and propylene glycol monophenyl ether acetate; dissolving 0.5 g to 20 g reducing agent in 10 mL to 200 mL solvent, to obtain a reducing agent solution, the reducing agent is alcohol amine-based reducing agent; homogeneously mixing the disperser solution obtained in the step with the silver salt dispersion obtained in the step with stirring at a constant speed in a range of 100 rpm to 500 rpm, to obtain a mixed solution; adding the reducing agent solution obtained in the step in droplets at a constant rate into the mixed solution obtained in the step with stirring and then reacting for a period of 120 min to 600 min at a temperature of 20 °C to 90 °C, to obtain a nano-silver particles dispersion; treating the nano-silver particles dispersion obtained in the step by cycling separation through ultrafiltration membranes, and then drying by centrifugal spray drying, to obtain a nano-silver powder. dispersing 1 g to 15 g silver salt precursor in 10 mL to 120 mL solvent, to obtain a silver salt dispersion; dissolving 1 g to 60 g disperser in 10 mL to 200 mL solvent, to obtain a disperser solution, the disperser being an acrylic-modified polyurethane-based disperser for water and weak solvents, the weak solvents being one or more selected from the group consisting of ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, di-propylene glycol monomethyl ether acetate, di-propylene glycol monoethyl ether acetate, di-propylene glycol monobutyl ether acetate, propylene glycol monoethyl ether acetate, di-ethylene glycol monomethyl ether acetate, di-ethylene glycol monoethyl ether acetate, di-ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl ether acetate, and propylene glycol monophenyl ether acetate; dissolving 0.5 g to 20 g reducing agent in 10 mL to 200 mL solvent, to obtain a reducing agent solution, the reducing agent is alcohol amine-based reducing agent; homogeneously mixing the disperser solution obtained in the step with the silver salt dispersion obtained in the step with stirring at a constant speed in a range of 100 rpm to 500 rpm, to obtain a mixed solution; adding the reducing agent solution obtained in the step in droplets at a constant rate into the mixed solution obtained in the step with stirring and then reacting for a period of 120 min to 600 min at a temperature of 20 °C to 90 °C, to obtain a nano-silver particles dispersion; treating the nano-silver particles dispersion obtained in the step by cycling separation through ultrafiltration membranes, and then drying by centrifugal spray drying, to obtain a nano-silver powder.