Catalyst auxiliary for FCC is a high-efficiency solid auxiliary that can significantly reduce sulfur oxides in flue gas in refinery catalytic cracking unit. It can effectively have a series of specific reactions with the sulfur in the flue gas, diverting it and turn it into H2S to reduce the sulfur content in the flue gas. When the addition amount reaches 5%, the sulfur oxides in the flue gas are reduced by 80%, and the product distribution of the catalytic cracking unit is not affected.