Taking the horizontal CNC machine as the research object, the thermal deformation tests of the machine tool spindle were conducted under the conditions of turning on the cooler and closing the cooler and the detailed analyses were carried out. The X, Y and Z axial thermal deformation laws of the spindle in two states were obtained. Then the solid model of the machine tool was established. The thermal deformation of the spindle part, the headstock part and the column component of the CNC machine tool were respectively analyzed by finite element thermosolid coupling and the fluidsolid coupling method. Then the main factor affecting the thermal deformation of the spindle was obtained.It provides basis for product improvement.