This paper focused on the isomerization and cracking of n-alkanes to synthesize bio-jet fuel. A series of SAPO-11 supports with different Si/Al molar ratio (0.2, 0.4, 0.6) were prepared, characterized, and evaluated by the hydroisomerization on hydrodeoxygenation product of castor oil. As a result, a Ni-Mo/SAPO-11(0.4) catalyst with hollow tubular structure and moderate acidic strength exhibited optimum conversion (97.2%) and jet fuel selectivity (81.6%) in the reaction. Subsequently, Ni-Mo/SAPO-11(0.4) was selected to carry out further experiments on studying the hydroisomerization and hydrocracking of long chain n-alkanes. The results show that increasing temperature may promote hydroisomerization and hydrocracking. Temperature is more favorable for the reaction with the length of the carbon chain decreasing, no matter conversion, hydrocracking degree or isomerization tendency. The product selectivity of different n-alkanes is associated with the carbon number. In reaction to n-C-18, Ni-Mo/SAPO(0.4) surpassed the other two catalysts in the conversion and i/n ratio at 623 K which is the optimum temperature.