The invention discloses a method for preparing nano copper powder in a micromolecular viscous medium. The method comprises the steps of: by taking a surface active agent, salt, a complexing agent, an antifoaming agent, an antioxidant, cupric salt, a reducing agent and deionized water as raw materials and according to the proportion of (0.001-95 percent) : (0.001-95 percent) : (0.001-80 percent): (0.001-75 percent): (0.001-70 percent): (0.001-75 percent): (0.001-70 percent): (0.001-98 percent), preparing the micromolecular viscous medium by using the surface active agent, the salt, the complexing agent, the antifoaming agent, the antioxidant and the deionized water; adding the cupric salt and uniformly mixing; adding the reducing agent and mixing; adding the deionized water to dilute so asto reduce the degree of viscosity according to a mass ratio of 1:0.5-10 of the total quantity of all materials abovementioned to the deionized water after the reaction completes; and obtaining nano copper powder through filter-pressing, deionized water washing, acetone washing and vacuum drying. According to the method disclosed by the invention, the raw materials selected in the invention are easily available, the manufacturing technique is simple and short, the production efficiency is high, the production cost and the energy compunction are low, and powder has low possibility of agglomeration and has good dispersibility, therefore the method is suitable for large-scale production and solves the problems of easy oxidation and easy agglomeration of the nano copper powder existing in the traditional chemical preparation method.