The measurement of solid-phase fraction (SPF) in solid-liquid two-phase flow is usually carried out on a horizontal pipe when using electrical resistance tomography technique. Due to the effect of gravity and viscous forces, solid objects are distributed in an uneven field in the cross-sectional pipe. However, the existing SPF computation method can be effectively used only in an even field, and the uneven distribution of solid objects will inevitably cause significant errors. In this paper, a SPF calculation method is proposed based on measurement decomposition and sensitivity coefficient reconstruction after analyzing the main features of typical flowing patterns under uneven distributions of solid object. By separating more effective parts from measurements and modifying sensitivity coefficients, the accuracy of the SPF calculation in the uneven distributions can be greatly improved. Experimental results show that the proposed method to calculate SPF can decrease both the maximal and the average errors to 8.2% and 4.5%, respectively. Therefore, the feasibility and effectiveness of the proposed method are demonstrated.