The texture of thin films is of wide concern because it can directly affect the properties and the applications of the film. The formation mechanism of the texture should be known first in order to control the character and content of the texture. On the basis of the empirical electron theory of solid and molecules and statistical mechanics, the formation of the texture of vapor-deposited fee thin film on polycrystal or amorphous substrate is explained with the calculation result of the valence electron structure of elements. Not only is the appearance of the (111) and (100) texture of the films convincingly explained, but the transformation order of random orientation--> (100) texture--> (100) + (111) texture--> (111) texture accompanying the rise of substrate temperature is also explained reasonably. The theory and method can also be used to explain the texture formation of films with other crystal structures.