Based on the CCAR-25-R4 “Airworthiness Standards of Transport Category Airplanes冶and FAA advisory AC25-7C“Flight Test Guide for Certification of Transport Category Airplanes”, this paper specifies the requirements of airworthiness and the classification of pilot induced oscillation (PIO). The paper also gives analysis on the flight test method of PIO and principles of flight test points' selection,the safety procedures during PIO flight test and evaluation criteria. The research can provide guidance for the PIO flight test of the civil airplanes.