In this study, the effects of shake amplitude, frequency, drum speed, and solid ratio of multi-gravity separator on ash content (AC) and combustible recovery (CR) of clean lignite were investigated and modeled. Experiments were planned by full factorial design and analysis of variance analysis is used to determine whether there are any significant parameters.As a result, mathematical models of AC and CR were derived as functions of studied parameters. At optimum conditions, the AC of clean lignite was reduced from about 75 to 50.81% with 58.71% CR. Additionally, the effect of drum speed was found to be higher than other parameters.