Aiming at the problem of fluidity loss and difficult construction caused by long distance and high temperature during the construction of self-compacting concrete for subway slab ballastless track, this paper studies the fluidity control technology of self-compacting concrete under different working conditions by simulating the slab filling experiment. The results show that when the underground haul distance is short (less than 5km), the self-compacting concrete can meet the construction requirements by using ordinary water reducer. When the underground haul distance is long (more than 5km), in order to ensure that the self-compacting concrete still has good flow properties, it is necessary to add super-retarding water reducing agent to meet the construction requirements. When the temperature is around 20°C, the self-compacting concrete mixed with 3.0% ordinary water reducing agent has good fluidity and meets the construction requirements. When the temperature is higher than 35℃, 2.8% retarder water reducing agent is added to improve the slump retention and fluidity of self-compacting concrete and meet the construction requirements.