Electrostrictive materials exhibit high induced strain under dc electric fields and this effect is important in generator application. This paper studied the energy-harvesting performances of La-doped PMN-PT electrostrictive ceramics that have rarely been reported. A multilayer structured electrostrictive energy harvester with high dielectric constant and electrostrictive coefficient is proposed. With a strain Sm = 7 × 10−5 (m/m), a peak current value of 630 µA is obtained across a small matched resistance of 450 Ω under a dc electrical field of 1.5 V/µm. The working principle of the device is reviewed and improved to predict the current and power generated by the harvester. Experimental results are compared to the theoretic behaviors of the improved model. A good agreement is observed by the two sets of data. The study on the efficiency of the energy conversion showed that a positive balance between the consumed power and the harvested power was presented by the device. The result demonstrates the potential perspective of the electrostrictive device in energy harvesting applied to low-power electronics.