Based on the definition of Wigner distribution function and Fresnel diffraction integral, the analytical expressions of Wigner distribution function of Lorentz beam on the waist plane, and on a plane in free space as well as on the exit reference plane of an ABCD system are derived. As their typical applications, the analytical expressions of the second-order moments of Lorentz beam are derived. The transformation rules of beam width and divergence angle of Lorentz beam are simulated and compared with those of the corresponding Gaussian beam. It is shown that Lorentz beam is a more appropriate model than Gaussian beam for diode laser beams.