Geometry optimization calculations were performed with different functional methods in density functional theory (DFT) at level 6-31G,and then^1H NMR calculations were performed with B3LYP/6-311++G^**level.The chemical shifts in the experimental ^1H NMR spectra were identified according to the changing trend of calculated ^1H NMR chemical shifts of baicalein, and the initial structure unit for crystal structure solution was determined by comparing the experimental with the calculated ^1H NMR spectra. The crystal structure of baicalein was determined directly from powder X-ray diffraction data using direct space approach and refined using Rietveld refinement techniques, and the result showed that the crystal structure of bacalein is monolinic,P21/c space group with cell parameters aof 0.787 351 nm,bof 1.333 318 nm,cof 1.165 971 nm,β of 100.150°,and Zof 4.
