Abstract: In the current trade settlement at Inner Mongolia power grid metering points, especially at the gateways of old thermal power plants, current transformers (CTs) of different models and manufacturers are often used separately at the generation-side and substation-side metering points. Due to differences in accuracy classes (e.g., Class 0.2S vs. Class 0.5S), the amplitude and phase of the secondary current output under the same primary current are not completely consistent, which leads to discrepancies in electric energy measurement for trade settlement. Moreover, since it is difficult to replace the generation-side CTs, economic issues such as over- or under-calculation of electricity fees arise. To address this problem, this paper proposes a compensation algorithm based on error characteristic analysis of current transformers. By establishing mathematical models of current ratio error and phase error, and developing a multi-load-point calibration and linear interpolation compensation strategy, the algorithm compensates for the accuracy differences among current transformers. Experimental verification shows that the proposed algorithm can reduce the power metering error caused by mismatched accuracy classes of current transformers, significantly improve the fairness and accuracy of trade settlement, and effectively safeguard the impartiality of power grid trade settlement.