In this paper

thermal analysis is narrated for two kinds of machine beds' simulating parts whose bending stiffnesses are not obviously equal under the condition of the thermal source similar to the environmental temperature or frictional heat. 3-D thermal conduction characteristics are discussed

and corresponding functional expression is also deduced. Moreover

temperature field distribution values are calculated by FEM program. The results show that they are near to the experimental values. Comparing machine beds’ simulating parts of small bending stiffness with those of large bending stiffness

the experimental results show that the former one's thermal geometrical precision is obviously better than the latter one′s. Therefore

in order to improve the structures of machine beds

for the first time

this paper puts forward the idea that the gravity deformation of the simulating parts of machine beds can automatically compensate the thermal deformation caused by variable environmental temperature or frictional heat by means of properly decreasing the curving stiffness of the simulating parts and eliminating the bondage of other parts to the deformation of the machine beds’ simulating parts. This principle provides a new method of eliminating basically thermal deformation of large-scale and precision machine tools.