Earthquakes are among the most serious natural disasters. The causes of earthquake are very complex，with trigger factors covering many fields of science.Scientists have been attempting to develop approaches for earthquake prediction for decades，with the aims being to define processes involved in earthquakes and to minimize the losses caused by earthquake disasters.Therefore，earthquake prediction has become an active area of research.Thus far，accurate and reliable earthquake prediction is still not possible，worldwide.The fundamental reason is that we have not fully mastered the mechanism，development，and occurrence processes.Fracture of materials acted on by cycling load is called fatigue.The damage process of materials under dynamic loading is known as fatigue process.The damage process of fatigue consists of initiation of cracks and rapid expansion of the cracks.The strata bear a cycling load due to the rotation of the earth and other seasonal factors.The crack of strata often appears due to damage process of fatigue under a variety of internal and external periodic dynamic loads.The damage process also consists of initiation cracks，confluence of cracks and expansion of cracks.This paper follows the theory of fatigue damage and the calculation method of dynamic signal fatigue damage energy.Fatigue failures are one of the most common failure models when the materials are burdened by cyclic loading.Furthermore，it is well known that nearly 80% of destruction of materials is due to fatigue.A mathematic calculation model of damage energy is conducted in this paper based on system analysis theory.With the model，the damage energy during the fatigue process can be calculated rapidly using a signal.The processes of fatigue failure are evaluated by this quantitative research.The results obtained in this paper will improve our understanding of seismic fatigue.We analyzed the seismic dynamic signals recorded at Putian seismic station in Fujian on August，2013 using theory of fatigue damage.A series of earthquakes occurred in August 2013 in the Putian area，with the Putian monitoring station being about 30 km from the epicenter. Signals corresponding to a series of earthquakes were acquired by the Putian station on a time interval of one hundredth of a second.The bearing capacity of rock fatigue damage was calculated，and shows that the calculated bearing rock fatigue damage energy has the following rules：（1） the fatigue damage energy of a rock formation changes with time.（2） Fatigue damage energy is circular before the earthquake，and the cycle for fatigue damage energy is one day （24 hours）.（3） the most obvious changes of fatigue damage energy occurred between 21:00 and 06:00 and between 12:00 and 15:00 Beijing time. （4） Earthquake magnitude was higher between 12:00 and 15:00，while fatigue damage energy was also higher before the earthquake.