The Great Reading of Qianlong in the Palace Museum is a masterpiece carefully drawn by the Italian court painter Lang Shining for Emperor Qianlong. It has superb artistic skills and reflects the prosperity of national strength and the high integration of Chinese and Western cultures during the Qianlong period. However, due to its huge scale, it has been difficult to display in the Palace Museum for a long time, which limits its due role. The most valuable part of the court painting in Qing Dynasty is the documentary painting by the court painter depicting contemporary figures and events, and The Big Moon Map belongs to this kind of painting. .