A harmonic distortion test is often used to check the dynamic linearity of ADCs. As the state-of-the-art ADCs have faster sampling rates, wider bandwidths and higher resolution, the input sine wave typically generated by an Arbitrary Waveform Generator (AWG) in ATE must be higher frequency with very lower distortion. Since AWG's circuit is designed to have the flexibility in terms of wave shapes, frequency and amplitude, it is difficult to output a very low distortion sine wave. The purpose of this paper is to introduce some techniques to generate the very low distortion sine wave by an AWG except very well know techniques like using LPF that cut off frequency is close to the output frequency.