Fertilizer, especially chemical fertilizer, contributes significantly to the production of modern agriculture. However, in recent years, fertilizer consumption has been increasing exponentially throughout the world, and as a result, causing a series of serious environmental problems. The use of water retaining slowly-release fertilizer (WRSRF) is a promising approach to improving the utilization of water resources and fertilizer nutrients, and pursuing sustainable development of the environment and agriculture. Some fertilizers can also be used to alleviate salt stress of crop plants, such as urea, manure, etc. however, little has been reported on application of water retaining slowly-release fertilizer to plants under salt stress. To fill the gas, a pot experiment was conducted to evaluate effects of WRSRF (ZL 2012 1 0400570.0) on plant morphology, root development, plant dry weight, leaf chlorophyll content, gas exchange parameters and water use efficiency (WUE) of rice seedlings under salt stress for 20, 40 and 80 d, separately. Rice seeds were sown in pots filled with natural soil, 2.68 g kg-1 in salinity. Twenty days later, half of the pots were amended with sodium chloride (NaCl) through irrigation to make 2.0 g kg^-1 in salinity. WRSRF was applied at 0, 1, 2 and 4 g kg^-1, separately to the pots. Results showed that: (1) growth of the rice seedlings applied with WRSRF increased with application rate of the fertilizer regardless of salt stress; (2) total root length, root surface area, root volume and number of root tips were all increased as EPSON scanning reveals, particularly in the treatment applied with WRSRF at 4% and the increase was especially significant in root surface area and root volume; (3) WRSRF application increased dry weight of the rice plants under salt stress, and the effect was more significant when WRSRF was higher in application rate. However, the stimulation effect was more obvious on roots than on shoots; (4) the fertilizer application increased leaf chlorophyll content of the plants under salt stress, and the increase was getting more significant with the experiment going on. However, the increase effect on chlorophyll content in plants under high salt stress was more obvious than that in plants under low salt stress; and (5) application of water retaining and slowly-release fertilizer promoted net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular carbon dioxide concentration (Ci), transpiration rate (Tr) and WUE, and these effects became more significant with increasing WRSFR rate, especially on Pn. However, application of the fertilizer decreased stomatal limitation values (Ls) of the plants, and the decrease became more significant with increasing fertilization rate. To sum up, application of the water retaining and slowly-release fertilizer (ZL 2012 1 0400570.0) may improve salt tolerance of rice seedlings significantly, which may be attributed to its effects on root growth, content of leaf chlorophyll, photosynthesis and WUE.