The invention relates to a method for increasing octane number of catalytically cracked gasoline. A catalytic cracking promoter used is prepared by adding ZSM-5 molecular sieve with silica-alumina ratio of 30-150, a carrier, a binder, phosphorus-containing compound and one or more of potassium, iron, magnesium, calcium and manganese into decationized water, and slurring and spraying for forming, or adding ZSM-5 molecular sieve with silica-alumina ratio of 30-150, a carrier, a binder and phosphorus-containing compound into decationized water, slurring and spraying for forming, and impregnating in or performing ion exchange with water solution of one or more of potassium, iron, magnesium, calcium and manganese; performing high-temperature calcination or high-temperature steam treatment to the product obtained from the above step; and loading or impregnating the product with zinc and one or more of molybdenum and tungsten. The promoter has good coke selectivity, can control liquefied gas yield, reduces gasoline yield loss, increases gasoline octane number and decreases gasoline olefin content.