This paper presents an analysis of acoustic emission (AE) detection technique for partial discharge (PD) on power transformer using piezoelectric sensor. The AE PD detection technique using piezoelectric material is one of the popular method due to its low cost and compact size. A matching resonant frequency of AE sensor with PD signal which in range 10 kHz to 300 kHz is an important factor for this technique. An AE sensor that have a resonant frequency match with PD signal able to give an optimal performances. Therefore, a simulation on different dimensions of lead zirconate titanate (PZT) AE sensor using finite element method (FEM) is conducted in order to determine the performances in terms of resonant frequency, total displacement and generated voltage. The length of AE sensor is varied from 2 mm to 30 mm in order to reveal the influence of length dimension against generated voltage. Based on the obtained results, that 2 mm length of AE sensor able to generate voltage of 3.01 x10-5 mV at resonant frequency of 113.58 kHz which can be proposed toward PD detection on the power transformer.