The invention relates to a preparation method for a J length/goat cashmere satin fabric. The mixed fabric is produced by 4/1 satin weaving of J length/goat cashmere 18.2 tex (70/30) and J length/goatcashmere 18.2 tex (70/30). The specific process of the method is that after warping, sizing and denting are conducted on J length/goat cashmere 18.2 tex warps, the J length/goat cashmere 18.2 tex warps are woven with J length/goat cashmere 18.2 tex wefts together, tensioning, arranging and winding are uniform in the warping process, a front, middle and rear subsection method is adopted to configure tension, so that four more grams of tension pieces are added to the side portion than the front area to increase tension; a sizing technology of 'double dipping, double pressing and double sizing boxes, middle pressure, high concentration, middle viscosity' is adopted in the sizing process, solid content of the size paste is 12 +/- 1%; a process configuration of 'small tension, large opening, high back rest and early opening' is adopted in the weaving process, temples of copper needles are adopted by the weaving machine, and the 4/1 J length/goat cashmere interwoven satin fabric is produced.