Gilsonite is a natural, brittle, and glisten tar hydrocarbon, which widely uses in the chemical, paint, and oil industry, besides asphalt production and thermal insulation. Major gangues of Gilsonite are gypsum, pyrite, silica, dolomite, cal-cite, and shale which are known as ash. Due to the fine liberation degree of gangue minerals from Gilsonite, most of the physical mineral processing methods are not applicable. Gilsonite has partially a behavior like coal in flota-tion due to its high carbon content and the similar composition of ash. As a result, flotation is one of the best methods to decrease the ash content of Gil-sonite. In this study, four factors i.e. the dosage of collector, frother, and de-pressant, and solid to liquid ratio in three levels were examined in flotation to reduce the ash content and increase the recovery of Gilsonite. These tests were designed with the Taguchi method by Design-Expert software. Our results showed the lowest ash content of 5.2% was obtained in the condition which 200 g/t Gasoil as collector, 100 g/t MIBC as a frother, 300 g/t sodium silicate as a depressant, and pulp density was 5% solid to liquid weight ratio.