PURPOSE: To obtain efficiently and industrially the titled yarn having improved physical properties, good feeling and high shrinkage percentage, by subjecting successively drawing, drying and relaxation of spun yarn, subjecting it further to shrinkage under pressurized steam and carrying out after-drawing under wet heat.

CONSTITUTION: A spinning stock solution consisting of an acrylonitrile copolymer containing ≥85wt% acrylonitrile is spun at 180W350m/min, preferably prepared undrawn yarn is put in a can once, collected to give 700,000W3,150,000 total de, the undrawn yarn is drawn in warm water at ≥80°C at 2W4 times draw ratio and washed. Then, the yearn is dried and relaxed at 140W170°C dry-bulb temperature and 80W90°C wet-bulb temperature, further subjected to shrinkage treatment with 1W4kg/cm2 pressurized steam and to after-drawing at normal pressure under wet heat at 1.5W2 times draw ratio to give the aimed yarn.