Abstract: This paper studies the process of alkali treatment of COPET/PA sea-island type composite fiber nonwovens and analyses the influences of alkali concentration,reaction time and temperature,and bath ratio on weight loss percentage and the relationship between the weight loss percentage and tensile strength.The research shows that alkali concentration and temperature are important factors affecting weight loss percentage and tensile strength.Generally,weight loss percentage increases with the increase of temperature,reaction time,and alkali concentration.The optimal alkali treatment parameters for sea-island fiber nonwovens are determined∶bath ratio,1∶40,alkali concentration,(10 g/L),treating at(95 ℃) for(30 min).