Our research of the representation theory of nonparaxial light beams and their physical properties such as a global parameter of a unit vector,the orbital angular momentum,the transverse effect,and the so-called spin Hall effect of light is introduced. On the basis of the plane-wave spectrum expansion,a representation formalism for finite beams is developed. After postulating a Jones vector that acts as a global quantity to represent the beam′s polarization,another global quantity,a unit vector is introduced. Both of the two global quantities are important in the representation formalism of finite beams. By using this formalism,the total angular momentum of an arbitrary free electromagnetic field is separated rigorously into spin and orbital parts,both of which are dependent on the state of polarization and the polarization ellipticity. In addition,the observed so-called spin Hall effect of light in both refraction and reflection is explained satisfactorily in terms of the change of the characteristic unit vector.