Abstract: The mine water in coal mines is an important unconventional water resource. The hierarchical treatment and quality-specific utilization of mine water are of great significance for alleviating the shortage of water resources in mining areas and protecting the ecological environment. Reverse osmosis desalination technology has been widely applied in the treatment projects of high-mineralization mine water due to its advantages such as mature technology and stable process. However, the desalination energy consumption of reverse osmosis technology increases significantly with the rise in the salt concentration of the treated feed liquid. Moreover, the total dissolved solids (TDS) content of the produced water is far lower than the limits of sulfate and chloride in Class III surface water (below 250 mg/L). This not only causes energy waste but also more easily triggers derivative problems such as a significant increase in the pressure of concentrated water discharge and aggravated membrane pollution. Based on this, a secondary modification strategy of moderately desalinated high-permeability reverse osmosis membranes is proposed for the actual desalination demand of mine water, and explores its technical-economic feasibility. Firstly, using self-prepared water as the raw water and aiming at a moderate decrease in desalination rate and a significant increase in permeability, the reverse osmosis flat membrane is chemically modified, and the optimal chemical contact time is determined to be 9 hours through membrane performance and quantified characterization indicators. Afterwards, based on the membrane test results, a chemical modification test is carried out on the 4040 membrane element, and the applicability of the modification strategy is verified under the self-prepared water and actual mine water systems. The results show that the online soaking chlorination conditions obtained from the flat membrane can be applied to the online chlorination treatment of the spiral wound membrane, and in the 168-hour long-term test with actual mine water as the raw water, the increase range of the membrane flux can reach up to 40% and the desalination rate remains continuously stable above 98%. Finally, by constructing an economic cost assessment model through the test results, it is confirmed that the desalination system based on the moderately desalinated high-permeability reverse osmosis membrane can realize the low-consumption treatment of mine water. Taking a daily production of 1000 m³ and a recovery rate of 15% as an example, under the condition of ensuring the same water production, assembling the modified membrane can reduce the original operating pressure from 1 to 0.755 MPa, and the energy consumption per ton of water decreases by 0.12 kWh/m³, which can effectively cover the expense of the secondary chemical modification. Therefore, the research aims to explore a moderately desalinated high-permeability reverse osmosis modification strategy suitable for the green fractionated treatment of coal mine water, and provide a new research idea for the development of the desalination process of highly mineralized mine water.