Abstract: We studied the relationship between cotton fiber properties and yarn tenacity by path analysis, and we found that the the upper half mean length , the bundle fiber tenac?ity, micronaire were the key indices for yarn tenac?ity, and proposed a new model of fiber quality index IFQI= (LE-10)/√MIC×STR on the studies at home and abroad, and constructed a new model FQI=LN（LE-18）/√MIC×STR, then we turned IFQI into IFQI_M= LE/√MIC×STR by high dimensional data fitting, these three models are of high prediction and good fitness, their structures are simple with less independent variables, fairly general and good mechanism, and can reflect cotton fiber properties and predict yarn tenacity.