In order to improve the numerical prediction skills for the atmospheric horizontal visibility (hereinafter referred to as "visibility") over sea surface associated with sea fog over the Yellow and Bohai Seas (the YBS), the A-F algorithm that calculates the visibility using air humidity information is constructed based on the surface observation data in foggy weather from 23 coastal and island stations of the YBS from 2013 to 2017, and then it is applied to numerical prediction of visibility associated with sea fog over the YBS. The results show that the A-F algorithm performs better than the SW algorithm (Stoelinga and Warner, 1999) which is commonly used to diagnose visibility using the model-predicted cloud water content. In particular, the A-F algorithm has the capability to diagnose light sea fog areas with visibility between 1 and 3 km that the SW algorithm always fails to forecast, indicating that the A-F algorithm has application value in the numerical prediction of visibility associated with sea fog over the YBS. The specific form of the visibility equation using the A-F algorithm can be further improved if putting in buoy and ship observations. It is possible to develop appropriate visibility algorithms for other seas according to the idea of constructing the A-F algorithm.