This paper aims to improve tone consistency for color electrophotography (EP). Color accuracy is crucial for printing. Calibrations are performed in EP printers to maintain consistent tone reproduction curves (TRCs). The calibration performance directly impacts the quality of color rendering. In this study, a model-based calibration approach is proposed to stabilize the TRCs. Regression models are developed to predict the primary color TRCs based on operating conditions and/or on-board sensor measurements. During a calibration, TRCs are predicted by the regression models, and the deviation is compensated by adjusting EP control parameters and modifying the tone correction mapping. The effectiveness of the proposed approach is validated using an off-the-shelf in-line four color EP printer under various environmental conditions and consumable factors. The experimental results demonstrate a 63.3% reduction in root-mean-squared error over the existing calibration method.