The present paper introduces the Automatic Waveform Selection (AWS) method for identifying the Electrostatic Solitary Waves (ESW) observed by Plasma Wave Instrument (PWI) onboard the Geotail spacecraft. Since the proposed method is based on the bit-pattern comparison, it does not require a lot of computer resources and the process speed is much faster than other pattern matching method using the First Fourier Transformation or the Wavelet transformation. We define the ESW index using the proposed AWS method. The ESW index allows us to perform statistical analyses by calculating it from a huge amount of Geotail data sets. We describe the detailed procedure of this new method for identifying the ESW waveforms and evaluate its efficiency. Further, we show one example of the statistical analyses conducted by using the AWS method, and discuss the result consulting the plasma electron measurements.