Lingyan temple is an important part of the Mount Tai World Natural and Cultural Heritage and was classified in 1982 as a national key cultural relic protection unit. There are many precious historical relics in Lingyan Temple, such as Pizhi Pagoda, the forest of stupas, stone inscriptions and many ancient buildings and ruins. Among the numerous precious historical relics, 40 painted Arhat statues of the Song and Ming Dynasties preserved in Qianfo Hall have higher artistic value. These polychrome statues, especially those from the Song Dynasty, were skillfully sculpted in the form of vivid and lifelike characters, recognized as rare masterpieces among ancient Chinese sculptures once praised as the first famous statues in China by Mr. Liang Qichao. However, over time, natural aging and environmental factors have brought various diseases to the statues, threatening their safe preservation. In August 2019, Shandong Cultural Relic Conservation and Restoration Center and Institute of Cultural Heritage of Shandong University launched the “Conservation and Restoration Project (Phase I) for Arhat Statues in Qianfo Hall of Lingyan Temple, Changqing, Shandong”. Disease investigations and research on disease causes and mechanisms are an important basis for the scientific protection of statues, and have great significance. In this study, X-ray diffraction (XRD), ion chromatography (IC), micro-Raman spectrometry (μ-RS), ultra depth-of-field microscopy, scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDX) and other analytical techniques, combined with related studies, were used to discuss the causes and mechanisms of various diseases of Arhat statues. The results show that the temperature in Qianfo Hall where the Arhat statues are located fluctuated frequently and greatly, and that the humidity in the hall has been high for a long time. The frequent fluctuations of temperature and humidity are one of the main factors that induced and aggravated various diseases of the statues. The main diseases of Arhat statues include surface pollution, efflorescence, paint layer flaking, cracking, falling off, insect damage, cranny and mutilation. Among these, surface pollution—dust and becoming covered with dirt—is the most common and widespread disease of these statues. The dust accumulation on the Arhat statue surfaces came from the raising of dust outside and inside the hall, and the dirt was formed by the mixing of insect excrement and surface dust. The appearance of insect damage, cranny and mutilation was less, and these diseases were only seen in some areas of several statues. There were more sulfates and nitrates in the efflorescent areas. The stress caused by the change of volume during the repeated crystallization and dissolution of sulfates broke the supporting layer and made it efflorescent. The efflorescence disease then caused the paint layer to flake, crack, and even fall off. The flaking and cracking diseases on statue foreheads, heads and other dusty areas were related to dust fall. The volume expansion stress caused by hydrous calcium sulfate formed by Ca²⁺ and SO2-₄ with water in the dust layer was transferred to the pigment layer, resulting in cracking and flaking. During this conservation and restoration project, we applied a variety of analytical techniques and referred to related research to explore the causes and mechanisms of Arhat statue disease. The purpose of this study is to provide basic research and a reference for the follow-up conservation and restoration of Arhat statues in Lingyan Temple and similar cultural relics.