Visual discomfort could be a significant issue in open-plan spaces with skylight. Due to the glazing size and position in the field of view (FOV) are different from that in perimeter area within side-lit rooms, the evaluation method generated from where may not be referenceable. Post-occupancy evaluation (POE) survey including subjective feedback collection and instrument measurements are taken place in an open-plan office building with skylights to assess the visual discomfort evaluation method in the specific scenario. Based on the research findings, a simulation-based retrofitting plan of skylights and windows is proposed. The results of the glare rating experiment indicate that DGI outperforms DGP in core areas or deep spaces while the glazing appeared in the central area of FOV, the borderline thresholds of DGP shift to lower values as the stimulus range is lower than that in perimeter spaces (e.g. low vertical eye illuminance). Under the situation that the glare sources appeared around the upper edge of FOV, simple luminance metrics which defined within the region surrounding the glare perform better. Moreover, a field test also confirmed that the preferred light level on the workplane under skylight ranges from 150 lx to 1000 lx. The findings refers to glare rating and daylight retrofitting design process may provide insights into visual discomfort issue in open-plan spaces with skylights.