The invention discloses a bidirectional high-thrust piezoelectric linear actuator and a driving method thereof. The high-thrust piezoelectric linear actuator mainly comprises a driving unit, a clamping unit and an output shaft; the upper piezoelectric stack and the lower piezoelectric stack are used as a driving source by adopting a symmetric structure design for the feature that the piezoelectricelement is compression resistant but not tension resistant, the upper piezoelectric stack and the lower piezoelectric stack respectively bear the driving of the pressure load and the tension load, thereby realizing the high-thrust bidirectional actuation. The clamping element comprises an upper clamping nut and a clamping nut, a flexible shaft coupler and a torque motor; the flexible shaft coupler transmits the torque motor to the clamping nut to realize different clamping. An output shaft is the trapezoidal lead screw, the teeth root is high, the abrasion resistance is good, the alignment isgood, and the manufacturability is good. The actuator disclosed by the invention is simple and compact in structure, the bidirectional helical clamping mechanism is used for matching the symmetrically distributed piezoelectric stacks, the single-step displacement of the stack is accumulatively accumulated, the high stroke and high thrust are output through the trapezoid lead screws, and the push-pull bidirectional actuation can be realized.