The invention discloses an antibacterial cotton textile fiber preparation method, which is characterized by comprising: immersing 5 g of a fabric in a caustic soda solution with a mass fraction of 5-30% for 15-60 min at a temperature of 20-35 DEG C, taking out the fabric, placing into 100 g of a chloroacetic acid aqueous solution with a mass concentration of 10%, taking out after 30-45 min, sealing the fabric in a polyethylene plastic bag, placing in a 30-80 DEG C oven, carrying out a reaction for 1-3 h, washing 3-5 times with 50 ml of an ethanol and water mixing solution with a volume ratio of 80:20, drying, dispersing 0.6 g of sodium alginate, 0.7 g of chitosan and 2.2 g of a coptis chinensis extract in 10 g of distilled water, carrying out mixing stirring for 15 min at a temperature of 30 DEG C to obtain the chitosan solution of microcapsule, immersing the modified cotton textile fiber in the chitosan solution of the microcapsule for 30-45 min, taking out, immersing 6 g of a modified starch cross-linking agent, carrying out a reaction for 0.5-1.5 h, adding 0.3 g of a material C, carrying out a reaction for 1 h at a temperature of 90 DEG C, drying for 5-15 min at a temperature of 150 DEG C, carrying out water washing 3-5 times, and drying so as to obtain the antibacterial textile. The prepared textile of the present invention has the lasting antibacterial effect.