In this work,a near infrared(NIR) spectroscopy was developed for detection of the chemical composition of flax fiber,as it had become a development trend to rapidly and accurately analyze the chemical composition of flax fiber used for spinning in the process of promoting the preparation and industrial production.Compared with the determination value by chemical analysis,a NIR model for the chemical composition was set up by partial least square method,which could be used in rapid and efficient quantitative analysis of the composition.Results showed that the correction correlation coefficient(RC) and the verification correlation coefficient(RCV) of the established NIR model for cellulose,hemicellulose,lignin and pectin were all above 0.9.The corrected root mean square error(RMSEC) was less than the predicted root mean square error(RESEP),and they both were smaller than 1.External verification and double tailed t test showed that the model prediction results were relatively accurate,and there was no significant difference between the predicted values and the measured values obtained by chemical analysis.Therefore,the NIR based model could be used for rapid prediction of the chemical composition of flax fiber.