Abstract: The elevation control of concrete bottom slab in curve line section of high-speed railway is difficult because fresh concrete cannot hold its shape and the slope of fresh concrete cannot maintain effectively before concrete hardening. To solve this problem, air-entraining agent and attapulgite clay were used to improve the thixotropy of fresh concrete. Results indicated when air-entraining agent and attapulgite clay incorporated simultaneously, the static yield stress of fresh concrete increased (10.28N·m), the dynamic yield stress decreased (5.47N·m), the ratio between the static and dynamic yield stress increased (1.9), and the ability of holding the shape and slope was improved (95.5%). Moreover, the pumping pressure was not increased obviously. The slope-holding rate of concrete bottom slab in curve line section on site reached more than 93% with air-entraining agent and attapulgite clay simultaneously added which was significantly better than that of fly ash concrete. This is mainly due to fibrous gel structure and orientation distribution of attapulgite clay and spherical air bubbles incorporated by air-entraining agent in fresh cement paste. These will provide valuable and useful references for quality control of concrete bottom slab in curve line section of ballastless track.