Based on the diffraction theory of beams in uniaxial crystals, diffraction properties of a Lorentz-Gauss beam in uniaxial crystals orthogonal to the optical axis are derived in analytical forms. Diffraction fields, intensity distributions and effects of beam parameters are investigated by numerical examples, respectively. Results show that, upon propagation, initial field components and intensity distributions of Lorentz-Gauss beams would deteriorate due to effects of anisotropic media. When the Lorentz-Gauss beam diffracts into the far field, its intensity distribution would convert into a four-petal profile. Beam parameters wx and wy are shown to have a strong influence on intensity distributions. By selecting different values of them, profiles of Lorentz-Gauss beams would be different upon propagation.