A piezoelectric actuator, comprising: a suspension plate, wherein the suspension plate is a square structure, a length of the suspension plate is in a range between 4mm and 8mm, and the suspension plate is permitted to undergo a curvy vibration from a middle portion to a periphery portion; a piezoelectric ceramic plate, wherein the piezoelectric ceramic plate is a square structure, a length of the piezoelectric ceramic plate is not larger than a length of the suspension plate, and the piezoelectric ceramic plate is attached on a first surface of the suspension plate, wherein when a voltage is applied to the piezoelectric ceramic plate, the suspension plate is driven to undergo the curvy vibration; an outer frame arranged around the suspension plate; and at least one bracket connected between the suspension plate and the outer frame for elastically supporting the suspension plate, wherein the bracket comprises: an intermediate part formed in a vacant space between the suspension plate and the outer frame and in parallel with the outer frame and the suspension plate; a first connecting part arranged between the intermediate part and the suspension plate; and a second connecting part arranged between the intermediate part and the outer frame, wherein the first connecting part and the second connecting part are opposed to each other and arranged along the same horizontal line. a suspension plate, wherein the suspension plate is a square structure, a length of the suspension plate is in a range between 4mm and 8mm, and the suspension plate is permitted to undergo a curvy vibration from a middle portion to a periphery portion; a piezoelectric ceramic plate, wherein the piezoelectric ceramic plate is a square structure, a length of the piezoelectric ceramic plate is not larger than a length of the suspension plate, and the piezoelectric ceramic plate is attached on a first surface of the suspension plate, wherein when a voltage is applied to the piezoelectric ceramic plate, the suspension plate is driven to undergo the curvy vibration; an outer frame arranged around the suspension plate; and at least one bracket connected between the suspension plate and the outer frame for elastically supporting the suspension plate, wherein the bracket comprises: an intermediate part formed in a vacant space between the suspension plate and the outer frame and in parallel with the outer frame and the suspension plate; a first connecting part arranged between the intermediate part and the suspension plate; and a second connecting part arranged between the intermediate part and the outer frame, wherein the first connecting part and the second connecting part are opposed to each other and arranged along the same horizontal line. an intermediate part formed in a vacant space between the suspension plate and the outer frame and in parallel with the outer frame and the suspension plate; a first connecting part arranged between the intermediate part and the suspension plate; and a second connecting part arranged between the intermediate part and the outer frame, wherein the first connecting part and the second connecting part are opposed to each other and arranged along the same horizontal line.