Abstract:Research purposes: CRTS III slab track is one of the main non - ballasted track type used in Chinese high speed railways. But at present，a little research has been devoted to the analysis of tlieir fatigue behavior. In order to research the fatigue characteristic of CRTS III slab track under temperature and train load，based on the load character of slab track，the 5 million cycle fatigue prototype test of CRTS III slab track witli pre - tensioning and post - tensioning prestressed slab was simultaneously conducted in this paper. The deformation of track components and the stress of slab was tested under the environmental temperature and cyclic train loading， at the same time，the change of cavity height beneath the track slab with the increased cyclic numberwas monitored in this experiment. Research conclusions ：( 1) The environment temperature has some influence on the vertical deformation of rail，while it has a significant influence on the vertical deformation at the end of slab，at a distance of 1/4 slab length from the end of slab，at the end of roadbed and the stress of slab. (2) With the increase of cyclic number of train loading，the stress of track slab，the vertical deformation of slab and roadbed both decrease in different degree. (3) The height of the cavity beneath the track slab changes slightly when the train load cycle number is less than 625 000，then it will distinctively increase witli the increased cycle number. (4 ) Comparing witli the post - tensioning prestressed slab track ； the influence of temperature and train load on the vertical deformation of slab ； the stress of slab and the cavity height beneatli the track slab is more significant for CRTS III slab track witli pre - tensioning slab. (5) The research results can provide the experimental basis for the design and maintenance of the CRTS III slab track.