n-decane and n-dodecane are important components in transport fuels and detailed combustion mechanisms with a large number of species and reactions applicable to combustion over a wide range of conditions have been developed. DRGASA and DRGEPSA are usually capable of achieving compact skeletal mechanisms, but they are too expensive since species are deleted in a one-by-one manner. An improved sensitivity analysis (SA) method is proposed in this work for skeletal mechanism reduction of large mechanisms. In this method pairs of strongly-coupled species are identified firstly and strongly-coupled species are treated like single species. In addition, species are deleted in an incremental manner in the improved SA method based on their sensitivity coefficients. Computational cost of this method is reduced significantly compared with the traditional SA methods. This improved SA method is employed to reduce the detailed mechanism of n-decane and n-dodecane with 2115 species and 8157 reactions. A skeletal mechanism with 126 species for n-decane obtained from a large size mechanism with 279 uncertain species and a skeletal mechanism with 162 species for n-dodecane based on a large size mechanism with 377 uncertain species are achieved with the improved SA. The skeletal mechanisms are further verified by comparing their important combustion characteristics with those of the detailed mechanism as well as experimental results. Our results show that the skeletal mechanisms can provide reasonable results compared with the detailed mechanisms. This indicates that the improved SA method is applicable to reduction of large-size mechanisms and compact and reliable skeletal mechanisms can be obtained. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.