Abstract: Reed widely grows in the arid and semi-arid regions in northwest China， which can purify nitrogen and phosphorus in water bodies. At present， there are few studies on the influence of both fluctuations of salinity and water level on the reed， so different combinations of salinity and water level fluctuations were set up to analyze their joint effects on nitrogen and phosphorus removal in water bodies. The results showed that low frequency increase of salinity (0.1g/L per 3 days) was beneficial to the removal of total nitrogen， total phosphorus and ammonia nitrogen， while high frequency increase of salinity (0.2g/L per 3 days) was unfavorable to them. The decline of water level is conducive to the removal of total nitrogen and ammonia nitrogen， the rise of water level plays a restraining role. The individual fluctuation of water level or salinity did not have a negative impact on the reed growth and its absorption of nitrogen and phosphorus. High frequent rise of water level and decline of salinity are more conducive to the accumulation of reed biomass， while both the decline of water level and salinity are conducive to the growth of reed roots. The dual fluctuations of water level and salinity directly affects the growth of reed， and indirectly affects the removal of nitrogen and phosphorus in water. The results may provide a reference for the formulation of water supplement schemes for rivers and lakes in arid and semi-arid regions in northwest China.