PURPOSE: To obtain a production process capable of improving the application efficiency of a finishing lubricant and decreasing the frequency of the formation of off-grade products caused by the drop of excess lubricant.

CONSTITUTION: In the production of a thermoplastic synthetic fiber by direct spinning and drawing process, the spun yarn filaments are coated with a spinning lubricant, drawn under heating with a fluid, subjected to the application of interlacing of ≥3/m with a fluid ejection nozzle and coated with a finishing lubricant.