The invention discloses a production technology for indigo cotton yarn. The production technology comprises the steps of blowing, carding, first drawing, second drawing, third drawing, roving, spinning and post processing, and specifically comprises the steps that firstly, indigo dye coating is molten to be prepared into a leuco body for use; secondly, preprocessed cotton is put into the indigo dye coating, the temperature is increased to 35 DEG C at a speed of 3 DEG C/min, temperature keeping is conducted for 30 min, the temperature is increased to 120 DEG C at a speed of 2 DEG C/min, dyeing continues to be conducted for 20 min, the temperature is decreased to 40 DEG C at a speed of 3 DEG C/min, and the cotton is taken out; thirdly, blowing, carding, first drawing, second drawing, third drawing, roving and spinning are conducted on the dyed cotton so that the cotton can be spun into cotton yarn for use; fourthly, post processing is conducted on the dyed cotton yarn, and post processing comprises drafty oxidation for 5 min, soaping and stoving, soap washing liquor is formed by adopting anhydrous sodium carbonate of 2 g/L and standard soap flakes of 5 g/L, the temperature is 60 DEG C, time is 20 min, and soap boiling, washing and stoving are conducted on the oxidized fabric.