We all know that uncertainty is unavoidable in all measurement results, and the reasonable uncertainty is enough to be measured to be worth the dispersion. Uncertainty is a parameter associated with the measurement results. This article mainly takes the measurement of the density of aluminum powder asphalt ship bottom paint as an example, evaluates the uncertainty of paint density detection according to JJF1056-1999, and analyzes and discusses the main factors that affect the specific gravity method to measure paint density, so as to give a better test work Guidance to improve the accuracy of measurement results.