Abstract: The changing dynamics of soluble protein, free amino acids and soluble sugar content in the stems, leaves and roots before plant bolting were studied to explore the effects of seedlings with different root diameters on plant bolting and physiological changes with the objective of providing a theoretical basis for Angelica sinensis nutritional control to restrain early bolting. The thicker the root diameter, the higher the soluble protein content in stems, leaves and roots before bolting. The soluble protein content initially increased, then decreased and finally increased in the stems and leaves, but the pattern was the reverse in the roots. Free amino acids in the stems and leaves decreased with an increase in seedling root diameter and in the roots, it increased before bolting plants appeared in the field, then decreased with fluctuations until some bolting plants appeared. Soluble sugar content increased with an increase in root diameter. It increased in both stems and leaves when the thinner root diameter seedlings were transplanted but it decreased rapidly after plant bolting in seedlings with thicker root diameters. During the growing period before bolting, low soluble protein and soluble sugar content, and high free amino acid content in the stems and leaves were not conducive to the occurrence of early bolting in plants with thinner root diameters, but otherwise promoted bolting.