Background and aims <p>Our previous researches showed that reed silicon (Si) accumulation positively responded to the groundwater depth (GD) changes, which was likely closely related to the involvement of Si in the nitrogen (N) metabolism. This study investigated the response relationship of reed Si and N accumulation with GD changes, the characteristics of photosynthetic parameters, and the indicators related to N metabolism, and explored the correlation between reed Si accumulation and indexes related to N metabolism under the changes of GD.</p> Methods <p>The characteristics of photosynthetic parameters (PPs), Si, N accumulation and the indicators related to N metabolism were studied through field sampling analysis.</p> Results <p>Results indicated that reed Si and N accumulation positively responded to GD changes, the correlation of reed Si accumulation with N accumulation was significant positive, and reed accumulated Si and N as physiological regulators and maintained relative stability of Si: N ratio (0.37–1.57) to cope with the changes of GD. The PPs, and the indicators related to N metabolism of reed were significantly affected by GD changes, and the correlation of these indicators ( key enzymes in N metabolism, chlorophyll and N-containing organic solutes, etc.) with reed Si accumulation and water use efficiency (WUE) were significant positive, indicating that reed Si accumulation indirectly regulated the N metabolism by improving WUE to alleviate water stress under the changes of GD.</p> Conclusions <p>These results indicate that Si and N accumulation play crucial roles in the drought resistance of reed, and the coupling effect of reed Si and N can provide theoretical reference for exploring effective technical measures for damaged ecosystems in desert oasis areas.</p>