With the electronic universal testing machine, the cyclic loading test on field sampling specimen of China railway track system(CRTS) Ⅰ slab track cement asphalt mortar（CA mortar） was conducted. All experiments were carried out in a servo controlled material testing system in which strain control was implemented. The results show that the ultimate compressive strength of CA mortar under monotonic loading is bigger than that under cyclic loading. The ultimate compressive strength of CA mortar of field sampling specimen is stronger than that of indoor specimen. And the strength of CA mortar will decline rapidly when the strength arrives to the ultimate strength because of accumulation of CA mortar damage under cyclic loading. The stress strain relationships for CRTSⅠ slab track CA mortar under cyclic loading are proposed by experimental study and analysis of parameters. The theoretical results of CA mortar are in good agreement with the experimental results.