An auto focus lens module with a piezoelectric actuator having a piezoelectric actuator, a tangent thrust element, a sliding fixture, a metal member, a guiding fixture, and a lens barrel is revealed. By a thrust in the tangent direction generated from the tangent thrust element toward the outer edge of the lens barrel, a friction is generated between the lens barrel and the piezoelectric actuator. When the piezoelectric actuator is applied with a voltage, the lens barrel driven by the piezoelectric actuator moves along an optical axis for focusing with the auxiliary of the guiding fixture. Due to fewer elements, light weight and compact volume, the design is applied to miniature auto focus lens modules so as to achieve effects of fast movement, stable focusing and reduced tilting.