The minor carpentry work of Gongshu Hall in Huyi District, Xi’an City, Shaanxi Province is an isolated structure of Tiangong Louge (halls and pavilions of the Heavenly Palace) described in Yingzao Fashi (State Building Standards). The polychrome paintings on this carpentry work are smooth, vivid and lifelike, and have been praised by scholars for their delicate craftsmanship. However, after more than six centuries, these paintings have suffered from blurring due to factors such as smoke deposition, discoloration, surface dust, and detachment of the ground layer, seriously affecting their visual integrity. To investigate the condition and production techniques, one representative polychrome painting was selected for non-destructive testing using X-ray radiography (XRR), infrared reflectography (IRR), and scanning macro X-Ray fluorescence (MA-XRF) imaging. The results revealed information about pigment composition, ink line drawing, and elemental distribution, providing new insights into the visual characteristics and production process from multiple perspectives. This work is of great significance for comprehensive understanding and scientific conservation of Gongshu Hall paintings, and offers valuable references for the detection and study of other wooden polychrome artworks.