The invention discloses a method for preparing a hydrophobic organosilicon/polyamide 6 block copolymer at original position taking end hydroxyl organic silicone oil, diisocyanate and epsilon-caprolactam as raw materials. The method comprises the following steps: adding the diisocyanate into melted dehydrated epsilon-caprolactam, adding the end hydroxyl organic silicone oil for carrying out a hydroxyl-isocyanic acid radical reaction after even mixing to generate end isocyanic acid radical organic silicone oil, then heating up the end isocyanic acid radical organic silicone oil to carry out thereaction of epsilon-caprolactam sealing the end isocyanic acid radical to obtain acylated caprolactam which contains the organic silicone oil and has the action of anionic polymerization catalysis promotion; and finally, adding an epsilon-caprolactam anionic polymerization catalyst to polymerize the rest epsilon-caprolactam to obtain the hydrophobic organosilicon/polyamide 6 block copolymer, wherein the weight ratio of the organic silicone oil to the polyamide 6 is between 4.5 and 40 to 100. The copolymer can be directly cast and formed or be mixed with polyamides for modification. The copolymer has the functions of improving the surface hydrophobicity of materials, and improving the surface lubricity and tenacity.