In this paper, spatio-velocity contrast sensitivity functions (SV-CSF) were measured by changing stimuli sizes and viewing distances, and a viewing-condition-dependent model of the SV-CSF are build based on these measured data. The viewing-condition-dependent SV-CSF model is particularly required to evaluate and improve moving image quality on large-sized flat panel displays. In the measurements, observers' thresholds of contrast sensitivities were obtained by subjective evaluations by 10 observers. From the experimental results, we found that the peak values of contrast sensitivities to stationary stimuli are varied with relative viewing distances. The relative viewing distance is a normalized distance by the size of display device. The highest peak of contrast sensitivities is observed at the viewing distance of three times size of display device. Based on these measured data, the viewing-condition-dependency of the SV-CSF is modeled as a concave function of the relative viewing distance.