Abstract: Improved analytic hierarchy process (IAHP) is introduced into determination of weight of landslide in risk assessment of oil tankfarm. Moreover, the three-demarcation method is deployed to replace the conventional ninedemarcation method, and the optimal transfer matrix is used to process the judgment matrix to eliminate the consistency check required by conventional hierarchy processes to determine the specific weight. In this way, convergence rate can be enhanced significantly. Additionally, Visual Studio C# 2010 is used for visualized IAHP software development. With references to domestic and overseas research documents and on-site investigation results, 10 indexes in risk assessment are chosen to determine the weights of landslip and the priority of specific index weights. The resulting priority is compared with the calculation results of fuzzy analytic hierarchy process (FAHP). Relevant results show that weights determined by IAHP and FAHP methods may vary in values, but the priorities are identical. It can be seen that the method may provide some guidance to determine the weight of landslide in risk assessment of the oil tankfarm.