Abstract: In theory, inverse geometry CT has the advantages of larger scanning field, higher signaltonoise ratio and fewer cone beam artifacts. However, in the multifocus and sparse angle scanning mode, the projection data also has some problems such as data truncation, sparseness and local redundancy. An inverse geometry MicroCT experimental system (IGMicroCT) with high resolution and large field of view was constructed by using electron beam scanning array micro multifocal Xray source and small area highresolution detector. In view of the characteristics of multifocal, sparse angle scanning mode projection data truncation and sparseness, a relative prior image guided SART iterative CT image reconstruction algorithm was proposed. Firstly, the algorithm was verified by simulation experiments, and the scanning parameters such as the number of ray source focus were optimized. Finally, highresolution MicroCT test images were obtained on the IGMicroCT experimental system. The experimental results show that the proposed algorithm can solve the problems of strip and truncation artifacts caused by projection data truncation, sparse sampling and local data redundancy. Besides, the feasibility of this new imaging method of IGMicroCT was verified, which lays a foundation for the practical application of IGMicroCT system.