Several methods are introduced to calculate the percolation threshold of nanoparticle cermet films made of ceramic matrix with embedded metal nanoparticles. For Ag-MgF2 nanoparticle cermet films, the percolation threshold of 0.14, which reasonably agrees with the experimental results, is calculated by using Priou's percolation threshold theory. The factors that affect cermet film percolation threshold are also discussed.