It is important to develop new promoters of fluid catalytic cracking (FCC) catalyst to increase iso-paraffin yield and avoid the decrease of research octane number (RON) caused by olefin saturation in gasoline hydrofining. SAPO-11 and LaAP0-11 molecular sieves were used as promoters to FCC catalyst to increase gasoline RON and were tested in the cracking reaction of n-dodecane on FCC conditions. LaAP0-11 molecular sieve has less and weaker acidity than SAPO-11 molecular sieve. LaAP0-11's metallic sites polarize the C H bonds to form carbenium ions for isomerization reaction and weak acid sites make less contributions to the cracking of iso-paraffin. LaAPO-11 promoter increases the yield of iso-paraffin (C5-9) from 6.4% to 10.2%. Besides that, a high yield of arene (2.0%) is caused by the dehydrogenation activity of LaAP0-11 promoter. The new contributions of this paper are the synthesis of a hydrothermal stable LaAP0-11 molecular sieve with isomerization activity and proposing the reaction routes of isoparaffin. These new contributions are important for developing more effective RON promoters of FCC catalyst. (C) 2018 Elsevier Inc. All rights reserved.