Abstract: This paper proposes a non-uniform sampling CT system based on equiangular multi-segment detectors,and derives a direct filtered back-projection (FBP) reconstruction algorithm for this system. It analyzes the limitations of the algorithm when dealing with non-uniformly sampled CT data,especially the impact of the non-smoothness of the weight function in the algorithm on reconstructed images. The theoretical derivation and simulation results of this work show that,although the direct FBP algorithm may lead to ring artifacts,these artifacts can be controlled within an acceptable range through appropriate system design,which making the FBP algorithm based on equiangular multi-segment detectors for non-uniformly sampled CT practical and capable of maintaining image resolution. The findings of this paper provide a theoretical basis and practical guidance for the design and optimization of new CT systems.