Spartina alterniflora is rapidly spreading along the southeast coast of China as an invasive species. However, the molecular mechanism of its adaptation via high tillering to salt environment is unclear yet. The objective of this study is to investigate the effect of salinity on the underlying mechanism of strigolactone (SLs) signaling-mediated tillering in S. alterniflora. The field transplant and greenhouse experiments were set up, while the tillering processes under different salinities were measured. The results showed that moderate (13-18‰, 15‰) salinity promoted the outgrowth of S. alterniflora tiller than control (0-6‰, 0‰) and high salinity (29-32‰, 30‰). Furthermore, the content of strigolactones (SLs) and the genes involved in SLs biosynthesis (D10, D17) ＆ signaling (D14, D53) were analyzed on the seedlings grown in greenhouse. The SLs content in roots was reduced with the increase of salinity, which resulted from the down-regulation of SaD10 and SaD17 expression. In addition, moderate salinity (15‰) down-regulated SaD14 and up-regulated SaD53 expression, while these gene expressions exhibited different under the control salinity (0‰) and high salinity (30‰). In conclusion, our data revealed that 15‰ salinity promoted the tillering process by depressing the SLs level via inhibiting SLs biosynthesis and perception, but activating the expression of a repressor in SLs signaling in S. alterniflora. The conclusion can help us to understand the mechanism of fast invasion of S. alterniflora into new intertidal salt habitats.