In order to further improve the forecast accuracy of fog visibility, a new fog visibility diagnostic scheme was established and tested based on the observational data of fog microphysics from April to July in 2008, May to August in 2009, May to September in 2011 at the Bright Summit of Mount Huangshan, and January to March in 2009 in Enshi, Hubei Province. First, previously developed visibility diagnostic schemes were compared and the importance of considering both liquid water content and droplet number concentration was confirmed in visibility schemes. Second, the coefficients in the previous diagnostic schemes are often taken as constants, but the close relationship between these coefficients and microphysics was found in this study. The relationships between the fitting coefficients and the droplet number concentration were established by half of Mount Huangshan’s data in 2008 and the visibility diagnostic schemes were improved. The effect of the new scheme has been verified by independent data, which include the other half of Mount Huangshan’s data in 2008, the whole of 2009 and 2011 and Enshi’s data in 2009.