Objective: To rapidly and quantitatively analyze the monoester alkaloids (MAs) in the extracting and concentrating process of Aconiti Radix Cocta (ARC) by near infrared spectroscopy (NIR). Methods: Using NIR to collect the data of 103 ARC samples and using partial least squares (PLS) regression method to establish the quantitative analysis model of MAs between the information of NIR and MAs. Results: The spectral range of MAs model of ARC was 9 264.35-7 274.11 cm-1. The root mean square error of cross validation (RMSECV) was 1.171 and correlation coefficient (r) of the calibration model was 0.999 4.Through the external validation, the root mean square error of prediction (RMSEP) was 1.321 and r of the validation model was 0.992 1. According to the results of statistical analysis, r of the predicted value and the reference value of MAs was 0.999 0. The value of P is less than 0.001. This revealed that the NIR and HPLC methods had a good correlation in determining MAs and could accurately predict the amount of MAs in the covered range. Conclusion: This method is convenient, rapid, accurate, and environment protective, and could be used for the on-line determination of MAs in the extracting and concentrating process of ARC and for the determination of the extraction and concentration endpoint of ARC.