A piezoelectric actuator, comprising a first level connector, a second level connector disposed opposite to the first level connector, a set of first piezoelectric material columns, a set of second piezoelectric material columns, and a set of third piezoelectric material columns, characterized in that the first level connector and the second level connector are both disc-shaped and of a certain thickness such that they are not deformed in operation; wherein the numbers of piezoelectric material columns in the first, second and third sets of piezoelectric material columns (131, 141, 151) are the same, each set has three piezoelectric material columns; wherein the three first piezoelectric material columns are spaced at equal angular separation along a circumferential line of the first and second level connectors (110, 120) and both ends of each of the first piezoelectric material columns are connected with the first level connector and the second level connector, respectively; wherein the three second piezoelectric material columns are spaced at equal angular separation along a circumferential line of the first and second level connectors (110, 120) and each of the second piezoelectric material columns has one end connected with the second level connector and the other end passes through 3 equally spaced through holes in the first level connector in a direction away from the second level connector so that the three second piezoelectric material columns and the second level connector are able to displace relative to the first level connector; wherein the three third piezoelectric material columns are spaced at equal angular separation along a circumferential line of the first and second level connectors (110, 120) and each of the third piezoelectric material columns has one end connected with the first level connector and the other end passes through 3 equally spaced holes in the second level connector in a direction away from the first level connector so that the three third piezoelectric material columns and the first level connector are able to displace relative to the second level connector; wherein during operation, the first piezoelectric material columns contract while the second and third piezoelectric material columns (141, 151) extend, or vice versa, so that the axial displacements of the three sets of piezoelectric material columns add up to produce the larger overall displacement of the actuator, wherein recesses are provided on opposite surfaces of the first level connector and the second level connector at locations where the first, second and third piezoelectric material columns (131, 141, 151) are connected and the first, second and third piezoelectric material columns (131, 141, 151) are bonded into the corresponding recesses. characterized in that the first level connector and the second level connector are both disc-shaped and of a certain thickness such that they are not deformed in operation; wherein the numbers of piezoelectric material columns in the first, second and third sets of piezoelectric material columns (131, 141, 151) are the same, each set has three piezoelectric material columns; wherein the three first piezoelectric material columns are spaced at equal angular separation along a circumferential line of the first and second level connectors (110, 120) and both ends of each of the first piezoelectric material columns are connected with the first level connector and the second level connector, respectively; wherein the three second piezoelectric material columns are spaced at equal angular separation along a circumferential line of the first and second level connectors (110, 120) and each of the second piezoelectric material columns has one end connected with the second level connector and the other end passes through 3 equally spaced through holes in the first level connector in a direction away from the second level connector so that the three second piezoelectric material columns and the second level connector are able to displace relative to the first level connector; wherein the three third piezoelectric material columns are spaced at equal angular separation along a circumferential line of the first and second level connectors (110, 120) and each of the third piezoelectric material columns has one end connected with the first level connector and the other end passes through 3 equally spaced holes in the second level connector in a direction away from the first level connector so that the three third piezoelectric material columns and the first level connector are able to displace relative to the second level connector; wherein during operation, the first piezoelectric material columns contract while the second and third piezoelectric material columns (141, 151) extend, or vice versa, so that the axial displacements of the three sets of piezoelectric material columns add up to produce the larger overall displacement of the actuator, wherein recesses are provided on opposite surfaces of the first level connector and the second level connector at locations where the first, second and third piezoelectric material columns (131, 141, 151) are connected and the first, second and third piezoelectric material columns (131, 141, 151) are bonded into the corresponding recesses.