Chromatic line confocal imaging (LCI) can be used in high-speed 3D imaging of surface morphology, roughness, and multi-layered transparent media in industrial production, quality inspection, and other fields. However, even if they are compensated for or corrected accordingly, the resolution of the built measurement system differs from the theoretical design. In particular, to guarantee high-speed measurement characteristics of the LCI system, a mass center algorithm with poor accuracy is usually chosen for peak extraction, and with the improvement of the manufacturing level, the axial resolution of the measurement system also puts forward higher requirements. Therefore, in this Letter, we propose a virtual double-slit differential dark-field chromatic LCI (VDSDD-LCI) technology. Our approach can reconstruct the optical 3D profile with higher axial resolution and signal-to-noise ratio (SNR) by reducing the full width at half maximums (FWHMs) of the axial response curve without changing the components of the completed LCI system. The experiments on a coin and scrive board surface demonstrate the validity of the proposed method.