The safety of Fengxian Temple at Longmen Grottoes has long been threatened by weathering and water seepage. An infrared imager was used to monitor the head area of the Ananda stone statue at Fengxian Temple and the water-seepage area on the south side of Locana Buddha for one year, and many infrared images were collected and analyzed using MATLAB image-processing techniques. The results show that there is a cyclic thermal stress caused by temperature difference at the fissure of the Buddha’s head. This temperature difference mainly comes from the difference in thermal conductivity between the grouting area and the rock; the change of thermal stress is the most significant around the morning of a sunny day. The temporal pattern of water seepage during the monitoring period was summarized, and the degree of water seepage in different areas was statistically calculated. The combination of infrared imaging and big data analysis was applied to the preventive conservation of the grottoes in order to achieve the image monitoring and statistical assessment of deterioration simultaneously. This work provides a reference for the monitoring and data analysis work at other grottoes.