Soda-AQ pulping with adding aluminum trioxide was studied to reveal the effect of silicon retention,and the mechanism of silicon retention was also discussed.The results showed that aluminum trioxide is able to restrain silicon transition from the pulp to black liquor es- pecially when the dosage of aluminum trioxide is more than 3%,and the contents of ash and silicon in the pulp increase correspondingly. Study on the mechanism showed that the pulp remains large amount of ash and silicon content probably ei...