Abstract: To study how pretreatment factors affect the air permeability of polyester filament fabric,the pretreatment pracess of the polyester filament fabric was simulated,varying the heat-setting temperature,tension and alkali concentration,and the air permeability of the fabric with different shrinkage and weight reduction rates are measured.The relation between the shrinkage,alkali weight reduction rate and air permeability was established by regression analysis.The relation between shrinkage and air permeability is a negative non-linear correlation,and that between alkali weight reduction rate and air permeability is a positive non-linear correlation.The air permeability was predicted by multi-analysis regression and BP neural network from the shrinkage and alkali weight reduction rate,the results show that prediction error is small as to both methods,while the method of BP neural network exhibits more precise.