Abstract: Alumina slurry suspensions of high solid content and low viscosity were prepared in the gelcasting process,it must be guaranteed that the filling ability of the ceramic size,in this process,the viscosity of the slurry is very important. So I design a set of three factors and three levels of orthogonal experiments which explore the effects of dispersant,PH and ball milling time on the viscosity of alumina ceramic slurry in the article. Through the experiment,it can be found that the content of dispersant is the biggest influence on the viscosity of ceramic slurry,therefore,I analyse separately the effect of dispersant on the viscosity of ceramic slurry by experiments. Finally,the research results of this paper is that the viscosity of ceramic slurry is the smallest when the dispersant is added into 2 wt%,the ball milling time is 2 hours,and when the pH is 9.