The invention discloses a 6000-mesh inorganic powder-filled modified PA (Polyamide)6 master batch and a preparation method thereof and belongs to the technical field of high-molecular materials. The PA6 master batch comprises the following main raw materials: PA6, a surface treating agent, polyethylene wax, paraffin wax and 6000-mesh inorganic powder, and the preparation method of the PA6 master batch comprises the following steps of: putting the 6000-mesh inorganic powder into a high-speed mixer for agitation and dehumidification, adding the surface treating agent for mixing and agitation and putting in a cold mixer for cooling, putting the PA6, the polyethylene wax and the paraffin wax into the high-speed mixer in sequence for mixing and agitation, adding the modified 6000-mesh inorganic powder for mixing and agitation, putting in the cold mixer for cooling and discharging and pelleting with an extruder to prepare the 6000-mesh inorganic powder-filled modified PA6 master batch. The 6000-mesh inorganic powder-filled modified PA6 master batch and the preparation method thereof have the beneficial effects that after the 6000-mesh inorganic powder-filled modified PA6 master batch is mixed with matrix resin, a whole system has good compatibility, dispersibility, flowability and processing performance, and a produced product has good mechanical property, dimension stability, toughness and impact resistance and the 6000-mesh inorganic powder-filled modified PA6 master batch is particularly suitable for manufacturing PA6 water supply pipes, PA6 double-walled corrugated tubes, plastic turnover boxes and automotive interior products.