An electrothermal actuator includes at least two operating portions and at least two electrodes. The at least two operating portions are electrically connected with each other to define at least one conductive path. Each of the at least two operating portions comprises a flexible polymer layer and a carbon nanotube paper. A thickness ratio of the carbon nanotube paper and the flexible polymer layer ranges from 1:7 to 1:10. A density of the carbon nanotube paper is greater than or equal to 0.5 g/cm3. A thermal expansion coefficient of the carbon nanotube paper is greater than or equal to ten times that of the flexible polymer layer. A conductivity of the carbon nanotube paper along a current direction of the at least two operating portions is in a range from about 1000 S/m to about 6000 S/m.