The aim of the paper was to study landfill leachate treatment efficiency during fermentation process in UASB reactor and post-treatment in RO process. In the first step of experiment, the granular sludge was acclimatized to treatment with high loaded synthetic wastewater. Next, the optimal concentration of raw leachate in synthetic wastewater was determined (5% v/v-40% v/v). At this stage, UASB reactor was operated at hydraulic retention time (HRT) of 7 days and organic loading rate (OLR) of 0.6 kg COD x m(-3) d(-1). While the optimal concentration of raw leachate in synthetic wastewater (20% v/v) was determined, the HRT was shortened from 7 to 2 days with a increase of OLR from 0.6 to 2.0 kg COD x m(-3)d(-1). The HRT (3 days) and OLR 1.3 kg COD x m(-3)d(-1) were taken as the optimum fermentation process parameters. Under such designed conditions COD removal achieved value of 76%. The concentration of COD, BOD, ammonia nitrogen, chloride concentration in effluent was kept on the level of 960 mg O-2 x dm(-3), 245 mg O-2 x dm(-3), 196 mg NH4+ x dm(-3) and 2350 mg Cl- x dm(-3) respectively. Due to poor quality of UASB effluent, wastewater was put into the post-treatment process. In RO process COD, BOD, chloride, ammonia nitrogen parameters were removed in 95.4%, 90.2%, 85.4% and 88.7% respectively.