Infrared thermography is a widely used nondestructive testing method in cultural relic protection. In current works,active infrared thermography is often used to evaluate cultural relics disease conditions and structural defects. In contrast,passive infrared thermography is not paid enough attention,and the dynamic relationship between cultural relics and their environment is rarely directly investigated. Taking the crack disease of Yuan Dynasty architectural murals in Fengguo Temple,Yixian County,Liaoning Province,as an example,this paper explored the feasibility of passive infrared thermography to study the cross-coupling effect between cultural relics and their existing environment. Based on obtaining more comprehensive information on the eave wall structure by taking thermal infrared images,continuous infrared thermography monitoring was carried out on the longitudinal long cracks in the middle of the east and west walls as well as the whole N1 mural of the north wall,and temperature measurement was carried out on the cracks,the ordinary wall surface and the wall surface where the wood keels located. Then,the cumulative anomaly and wavelet analysis methods were used to analyze the changing trend and periodic temperature fluctuation at these characteristic positions. The monitoring and analysis results were qualitatively discussed from the perspective of heat transfer,and the influence modes at different positions of the mural were distinguished. Combined with the characteristics of the cracks,the formation process was preliminarily judged. The results show that the mural has an uneven multi-layer structure,and there are differences in the heat transfer pathway and structural strength. The temperature trends of the east and west walls are similar,but there are obvious differences in fluctuation signal and energy. The overall fluctuation energy of cracks is greater than that of walls and is positively correlated with the degree of development of the cracks. The fluctuation energy of the first main cycle comes from the diurnal variation of temperature. In contrast,the secondary main cycles may be related to random disturbances in the heat transfer process. The energy fluctuation during the daytime and after sunset plays a key role in the heat transfer effect. The heat transfer process at the wood keels and the cracks is faster,so the high-temperature centre and the transverse heat transfer trend are formed over time. The occurrence of crack disease results from the mechanical strain differences of material under the influence of temperature change. There are two heat transfer pathways:one is the heat conduction with the eave wall as the medium,and the other is the convective heat transfer through the air channel at the eave column; the former mainly induces the formation of several parallel transverse short crack groups in the units,while the latter promotes the formation of longitudinal long cracks at the eave columns. This paper can provide a reference for evaluating the heat transfer process of other cultural relics in complex environments.