Abstract: Taking Spartina alterniflora distributed in Eastern Fujian coastal wetlands as the research object. In the field, a 3-month castration plus different shading tests were conducted to determine the biomass, free proline, soluble sugar and soluble protein content of S. alterniflora. The variation of biomass and osmotic adjustment substances of different shades of S. alterniflora was analyzed. The results show that Different shading rates have a significant effect on the biomass and osmotic adjustment substances of S. alterniflora. With the increase of shading intensity, the biomass, soluble sugar and soluble protein content of S. alterniflora are decreasing, and free proline shows an increasing trend. The leaf shading biomass, stem biomass, sample biomass, soluble sugar and soluble protein content of different shading rates reach the minimum at 90% shading treatment, which are 2.12, 3.64, 474.83 g, 9.89 mg/g and 15.48 mg/g respectively, accounting for 43.35%, 39.95%, 45.16%, 33.83%, 33.04% of CK, respectively. The free proline content reaches a minimum of 58.42 μg/g at 30% shading and a maximum of 241.59 μg/g at 90% shading, indicating high-intensity shading on S. alterniflora biomass and osmotic adjustment substances. The effect is more significant and can greatly inhibit the rapid growth of S. alterniflora. In addition to the 30% shading treatment, the shading treatment of S. alterniflora biomass, soluble sugar, soluble protein and free proline content ae significantly different from those of the same period.