Abstract: Supraharmonic pollution has become a great concern with increasing modern energy efficient appliances connected into power grid. Determining responsibility is the premise for controlling and managing supraharmonic. Since harmonics of a point of common coupling (PCC) are commonly produced by both system side and customer side, it is important to determine which side is the dominant harmonic source. Considering both sides of harmonic current source are approximately independent, the complex independent component analysis (Complex ICA) method is used to obtain the mixed matrix and supraharmonic impedance of both sides. This paper proposes a new index for judging dominant supraharmonic source by vector projection technique. Project the harmonic voltage, that the supraharmonic source of the system side and the customer side respectively acts, to the measured voltage of the PCC. By comparing the value of the projection, if the value of one side is larger than half of the supraharmonic voltage of the PCC, it can be considered to be the dominant harmonic source. The method can qualitatively determine the position of the main supraharmonic source, which provides new ideas for the supraharmonic source tracing. Validity and effectiveness are verified by simulation and actual field data analysis.