Unique optical properties of the simple lens composed of left-handed material (LHM) are reasonedly studied here according to Geometrical Optics. Analytic calculation of the negative refraction at the spherical surface is conducted demonstrating that the usual optical formulas still hold true for the LHM lens. The inherent merits of the LHM lenses are discussed comparing to their counterparts made of right-handed material (RHM). Finally,single thin LHM lens with a complete correction of spherical aberration is verified and a practical example is presented accordingly.