A novel pretreatment process for Reverse Osmosis concentrate was proposed which consisted of chemical removal of hard ions,coagulation and sedimentation,ions exchanges and ultrafiltration.Experiments were carried out to study the effects of pretreatment process onthe removal of Ca2+,Mg2+and SiO32-and to the performance of the air gap membrane distillation (AGMD).The results showed that the contents of Ca2+, Mg2+and SiO32-were all below 5 ppm.Moreover,the insoluble salts such as CaCO3and Mg(OH)2 were unsaturated in the AGMD process.As a result, CaCO3 and Mg(OH)2would not deposit on the surface of the membrane when the RO concentrate wasprocessed in the AGMD module.After pretreatment ,the main substance in the RO concentrate is NaCl which could be concentrated to crystalline form to obtain NaCl solid.When the concentrate factor reached 7,the novel pretreatment process could increase the permeate flux by 24.02%,the conductivity maintainedrelatively stableand the CODCr of the permeate was below 10mg/l.As results,the permeate of the process could be used as circulating cooling water and washing water in industry. Moreover, after absorbed by activated carbon, the permeate water could be used as boiler water. The pretreated RO concentratewas concentrated continuously for 168 hours via AGMD.During the process, the permeate flux decreased slowly, the conductivity of the permeate was below 5μS/cm and the CODCr of the permeate was below 10 mg/l.