The invention discloses a lixiviating method of a liquid ammonia water solution after a mercerization process. Under the tensioning condition, fabrics are soaked into an NaOH solution to be treated, wherein the concentration of the NaOH solution is 230g/L to 250g/L; the processing temperature is controlled to be 17 DEG C to 22 DEG C; the treatment is performed for 4 to 6 minutes; the fabrics are taken out and are dried through being extruded; the fabrics are washed for 5 to 20 times in the liquid ammonia water solution of which the water content is 1 percent to 12 percent; the washing lasts 8 to 12 minutes each time; the lixiviating effect is achieved. The lixiviating method has the beneficial effect that the liquid ammonia water solution can be used for washing NaOH molecules in ramee fiber subjected to mercerization by concentrated alkaline.