The near-infrared (NIR) band assignment of Tanshinone ⅡA and Cryptotanshinone were performed by 2D-COS technique in deuterated chloroform. According to the two-dimensional synchronous slice spectra of Tanshinone ⅡA and Cryptotanshinone, Tanshinone ⅡA and Cryptotanshinone have characteristic absorption at 1 600~1 800, 1 900~2 230, and 2 300~2 400 nm. Tanshinone ⅡA has characteristic bands at 1 640 and 2 140 nm which connected with the first double-frequency and combination frequency of furan ring double bond. 1 696 nm was the second double-frequency of methyl stretching vibration in Tanshinone ⅡA and Cryptotanshinone molecules, the absorption at 1 726 and 1 740 nm were the second double-frequency of Tanshinone ⅡA and Cryptotanshinone which connected with cyclohexene methylene stretching vibration, 2 146 and 2 220 nm were the combined frequency of Tanshinone ⅡA and Cryptotanshinone which linked with benzene ring C—C and C—H stretching vibration, a series of peaks at 2 300~2 400 nm were the combination frequencies of stretching vibration and bending vibration of methyl in Tanshinone ⅡA and Cryptotanshinone molecules. Taking Tanshinone Extract as a carrier, the characteristic band by 2D-COS and the band by synergy interval Partial Least Squares (SiPLS) were used to establish Partial Least Square (PLS) quantitative models. The coefficients of determination R² were all greater than 0.9, the Root Mean of Square Error of Calibration (RMSEC) and Root Mean of Square Error of Cross-Validation (RMSECV), and the Root Mean of Square Error of Prediction (RMSEP) were very small. The results showed that the PLS model established by 2D-COS and SiPLS were both good. The quantitative model based on the 2D-COS technique was explanatory. 2D-COS can be used to analyze the characteristic absorption connected with a structural differences. The simultaneous quantitative determination of structural analogues can be realized in the same band.