Accuracy and speed are important indicators to detect the image reconstruction algorithm for electrical capacitance tomography. In recent years，although many image reconstruction algorithms have been studied，they can not achieve desired results. Aiming at the problem of image reconstruction，in this paper，image reconstruction algorithm based on spectral projection gradient algorithm for electrical capacitance tomography system is carried out． The algorithm combines the principle of ECT，direction tracking regard as a target，updating direction and step size are on spectral projection gradient． To avoid the local optimal solution，induce non- monotonic search strategy is introduced to balance the accuracy and speed. Simulation experiment of typical flow pattern is carried out by the algorithm，and compared with the traditional LBP algorithm. The results show that the reconstruction accuracy of the proposed algorithm is improved. This method provides a new research perspective for ECT image reconstruction.