Abstract: With aluminium asphalt ship bottom paint as example, the uncertainty of density measurement of coatings was evaluated according to JJF 1059-1999. The results show that the density of the coating ρ23 ℃=1.227 6 g·mL-1, the related expanded uncertainty Urel=0.05%, the expanded uncertainty U=0.000 7 g·mL-1, and the coverage factor k=2. The obtained measurement uncertainty of the coating was lower one order of magnitude than that given in GB/T 6750-2007 “Paints and Varnishes-Determination of Density-Pyknometer Method”.