LF-NMR was used to study the internal water state of Salvia miltiorrhiza in the process of infiltration or drying,and the migration rule before and after processing was analyzed.This study provides a scientific method for water control of rhizoma.The color value of S. miltiorrhiza was determined by color difference technique.The chemical mechanism of S. miltiorrhiza processing was described from the perspective of color and moisture.The results show that the internal water of S. miltiorrhiza can be divided into two states,free water and bound water.The free water content of S. miltiorrhiza in dry condition was 2.02%,and about 88.76% after 6 h infiltration.Under the condition of fresh root of S. miltiorrhiza,the free water content was about 97.74%,the drying point reached 24 h at 50 ℃,and the inner bound water content was about 6.82%.The signal has a good correlation with the water quality,and the relaxation peak area can be used to obtain the water distribution during the processing of traditional Chinese medicine.The results of relaxation peak area and color difference indicated that there was a correlation between water content and appearance.