Abstract: Based on considering the effect of slab steel elastic modulus, thermal conductivity, specific heat capacity and linear expansion coefficient on simulation precision, the simulation of stress field and temperature field of steel Q345C 250 mm x 1500 mm single-piece casting slab during cooling process has been carried out by ABAQUS finite element analysis software to get the relative information between stress ( <20 ~ 148 MPa) , temperature (769 ~ 1 000 °C ) and time (0 ~ 1 200 s). Calculated results show that the distribution of temperature of slab along width direction during cooling process is not uniform, the cooling rate of slab surface edge is 0. 46 °C  /s, but the slab distance from slab surface edge more than 200 mm basically has same cooling rate (0. 23  °C /s) ； the cooling rate of slab stacking is rather low, it is about 15 °C  /h, which conforms to measuring results in situ. The convey time from flame cut off machine for casting slab to heating furnace decreases to minimum with adopted holding measures to prevent defects formation being due to excessive thermal stress at slab surface.